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‎Array and String Manipulation.ipynb‎

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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Question 1: Count Negative Numbers in a Sorted Matrix, by Amazon and Apple\n",
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"- Given a m x n matrix grid which is sorted in non-increasing order both row-wise and column-wise, return the number of negative numbers in grid.\n",
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"- https://leetcode.com/problems/count-negative-numbers-in-a-sorted-matrix/"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 14,
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"8"
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]
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},
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"execution_count": 14,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"# solution 1: brutal force \n",
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"def countNegatives(grid):\n",
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" count =0 \n",
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" for i in range(len(grid)):\n",
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" for j in range(len(grid[0])):\n",
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" if grid[i][j]<0:\n",
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" count+=1\n",
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" return count\n",
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"\n",
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"# test case \n",
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"grid = [[4,3,2,-1],[3,2,1,-1],[1,1,-1,-2],[-1,-1,-2,-3]]\n",
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"countNegatives(grid)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 15,
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"8"
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]
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},
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"execution_count": 15,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"# solution 2: import package \n",
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"def countNegatives(grid):\n",
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" import numpy as np\n",
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" count = 0 \n",
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" grip = np.array(grid)\n",
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" result = grip.flatten()\n",
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" for i in result:\n",
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" if i < 0:\n",
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" count+=1\n",
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" return count\n",
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"\n",
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"# test case \n",
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"grid = [[4,3,2,-1],[3,2,1,-1],[1,1,-1,-2],[-1,-1,-2,-3]]\n",
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"countNegatives(grid)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 21,
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"8"
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]
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},
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"execution_count": 21,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"# solution 3: binary search \n",
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"def countNegatives(grid):\n",
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" \n",
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" n = len(grid[0])-1 # column numbers\n",
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" \n",
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" count = 0 # initialize the count\n",
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" \n",
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" for row in grid: # iterate over the rows\n",
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" \n",
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" low, high = 0, n # set searching space: low and high\n",
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" \n",
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" while low <= high: # while the condition is met\n",
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" \n",
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" mid = low + (high-low)//2 # set the third search space: middle \n",
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" \n",
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" if row[mid] > -1: # if the selected value is bigger than -1\n",
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" low = mid + 1 # move the searching space to the right \n",
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" \n",
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" else: # if the selected value is smaller than or equal to -1: \n",
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" high = mid - 1 # move the searching space to the left\n",
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"\n",
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" if low <= n: # outside the while loop, we compare the leftmost searching point to n\n",
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" count += (n+1)-low # everything on the right side of low is negative\n",
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" \n",
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" return count\n",
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" \n",
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"# test case \n",
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"grid = [[4,3,2,-1],[3,2,1,-1],[1,1,-1,-2],[-1,-1,-2,-3]]\n",
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"countNegatives(grid)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"---"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Question 2: Replace Elements with Greatest Element on Right Side, by Amazon\n",
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"- Given an array arr, replace every element in that array with the greatest element among the elements to its right, and replace the last element with -1.\n",
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"- After doing so, return the array.\n",
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"- https://leetcode.com/problems/replace-elements-with-greatest-element-on-right-side/"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 17,
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"[18, 6, 6, 6, 1, -1]"
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]
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},
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"execution_count": 17,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"# solution 1: brutal force\n",
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"def replaceElements(arr):\n",
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" \n",
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" new = []\n",
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" \n",
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" for i in range(len(arr)-1):\n",
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" new.append(max(arr[i+1:]))\n",
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" \n",
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" new +=[-1]\n",
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" \n",
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" return new\n",
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"\n",
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"#test case \n",
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"arr = [17,18,5,4,6,1]\n",
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"replaceElements(arr)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 11,
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"[18, 6, 6, 6, 1, -1]"
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]
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},
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"execution_count": 11,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"# solution 2: \n",
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"def replaceElements(arr):\n",
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" max_value = -1 \n",
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" for i in range(len(arr)-1,-1,-1):\n",
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" arr[i],max_value = max_value,max(max_value,arr[i])\n",
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" return arr\n",
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"\n",
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"#test case \n",
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"arr = [17,18,5,4,6,1]\n",
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"replaceElements(arr)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"----"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Question 3: Three Consecutive Odds, by Dajiang \n",
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"- Given an integer array arr, return true if there are three consecutive odd numbers in the array. Otherwise, return false.\n",
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"- https://leetcode.com/problems/three-consecutive-odds/"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 23,
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"False"
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]
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},
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"execution_count": 23,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"# solution 1: brutal force\n",
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"def three_consecutive_odds(arr):\n",
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" for i in range(len(arr)-2):\n",
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" if arr[i]%2 != 0 and arr[i+1]%2 != 0 and arr[i+2]%2 != 0:\n",
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" return True\n",
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" else: # extra attention: the position/indentation of else!\n",
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" return False\n",
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" \n",
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"# test case \n",
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"arr = [2,6,4,1]\n",
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"three_consecutive_odds(arr)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 24,
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"metadata": {},
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"outputs": [
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{
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"data": {
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"text/plain": [
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"False"
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]
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},
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"execution_count": 24,
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"metadata": {},
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"output_type": "execute_result"
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}
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],
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"source": [
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"# solution 2 \n",
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"def three_consecutive_odds(arr):\n",
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" count=0\n",
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" for i in range(len(arr)):\n",
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" if arr[i]%2 != 0:\n",
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" count+=1\n",
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" \n",
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" else:\n",
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" count =0 \n",
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" \n",
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" if count==3:\n",
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" return True\n",
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" \n",
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" else: # extra attention: the position/indentation of else!\n",
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" return False\n",
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" \n",
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"# test case \n",
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"arr = [2,6,4,1]\n",
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"three_consecutive_odds(arr)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"----"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.7.4"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 2
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}

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