|
| 1 | +{ |
| 2 | + "cells": [ |
| 3 | + { |
| 4 | + "cell_type": "markdown", |
| 5 | + "metadata": {}, |
| 6 | + "source": [ |
| 7 | + "# Question 1: Remove All Adjacent Duplicates In String, by Facebook, Amazon, Bloomberg, Oracle\n", |
| 8 | + "- Given a string S of lowercase letters, a duplicate removal consists of choosing two adjacent and equal letters, and removing them.\n", |
| 9 | + "- We repeatedly make duplicate removals on S until we no longer can.\n", |
| 10 | + "- Return the final string after all such duplicate removals have been made. It is guaranteed the answer is unique.\n", |
| 11 | + "- https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/" |
| 12 | + ] |
| 13 | + }, |
| 14 | + { |
| 15 | + "cell_type": "code", |
| 16 | + "execution_count": 12, |
| 17 | + "metadata": {}, |
| 18 | + "outputs": [ |
| 19 | + { |
| 20 | + "data": { |
| 21 | + "text/plain": [ |
| 22 | + "'ca'" |
| 23 | + ] |
| 24 | + }, |
| 25 | + "execution_count": 12, |
| 26 | + "metadata": {}, |
| 27 | + "output_type": "execute_result" |
| 28 | + } |
| 29 | + ], |
| 30 | + "source": [ |
| 31 | + "def removeDuplicates(S):\n", |
| 32 | + " list_1 = []\n", |
| 33 | + " for i in S:\n", |
| 34 | + " if list_1 and i==list_1[-1]:\n", |
| 35 | + " list_1.pop()\n", |
| 36 | + " else:\n", |
| 37 | + " list_1.append(i)\n", |
| 38 | + " return \"\".join(list_1)\n", |
| 39 | + "\n", |
| 40 | + "# test case \n", |
| 41 | + "S = \"abbaca\"\n", |
| 42 | + "removeDuplicates(S)" |
| 43 | + ] |
| 44 | + }, |
| 45 | + { |
| 46 | + "cell_type": "markdown", |
| 47 | + "metadata": {}, |
| 48 | + "source": [ |
| 49 | + "----" |
| 50 | + ] |
| 51 | + }, |
| 52 | + { |
| 53 | + "cell_type": "markdown", |
| 54 | + "metadata": {}, |
| 55 | + "source": [ |
| 56 | + "# Question 2: Make The String Great, by Google\n", |
| 57 | + "- Given a string s of lower and upper case English letters.\n", |
| 58 | + "- A good string is a string which doesn't have two adjacent characters s[i] and s[i + 1] where: 0 <= i <= s.length - 2\n", |
| 59 | + "- s[i] is a lower-case letter and s[i + 1] is the same letter but in upper-case or vice-versa.\n", |
| 60 | + "- To make the string good, you can choose two adjacent characters that make the string bad and remove them. You can keep doing this until the string becomes good.\n", |
| 61 | + "- Return the string after making it good. The answer is guaranteed to be unique under the given constraints.\n", |
| 62 | + "- Notice that an empty string is also good.\n", |
| 63 | + "- https://leetcode.com/problems/make-the-string-great/" |
| 64 | + ] |
| 65 | + }, |
| 66 | + { |
| 67 | + "cell_type": "code", |
| 68 | + "execution_count": 13, |
| 69 | + "metadata": {}, |
| 70 | + "outputs": [ |
| 71 | + { |
| 72 | + "data": { |
| 73 | + "text/plain": [ |
| 74 | + "'leetcode'" |
| 75 | + ] |
| 76 | + }, |
| 77 | + "execution_count": 13, |
| 78 | + "metadata": {}, |
| 79 | + "output_type": "execute_result" |
| 80 | + } |
| 81 | + ], |
| 82 | + "source": [ |
| 83 | + "# solution 1\n", |
| 84 | + "def makeGood(s):\n", |
| 85 | + " stack = []\n", |
| 86 | + " for i in s: \n", |
| 87 | + " if stack and stack[-1] != i and stack[-1].lower() == i.lower():\n", |
| 88 | + " stack.pop()\n", |
| 89 | + " else:\n", |
| 90 | + " stack.append(i)\n", |
| 91 | + " return \"\".join(stack)\n", |
| 92 | + "\n", |
| 93 | + "#test case\n", |
| 94 | + "s = 'leEeetcode'\n", |
| 95 | + "makeGood(s)" |
| 96 | + ] |
| 97 | + }, |
| 98 | + { |
| 99 | + "cell_type": "code", |
| 100 | + "execution_count": 14, |
| 101 | + "metadata": {}, |
| 102 | + "outputs": [ |
| 103 | + { |
| 104 | + "data": { |
| 105 | + "text/plain": [ |
| 106 | + "'leetcode'" |
| 107 | + ] |
| 108 | + }, |
| 109 | + "execution_count": 14, |
| 110 | + "metadata": {}, |
| 111 | + "output_type": "execute_result" |
| 112 | + } |
| 113 | + ], |
| 114 | + "source": [ |
| 115 | + "# solution 2\n", |
| 116 | + "def makeGood(s):\n", |
| 117 | + " stack = []\n", |
| 118 | + " \n", |
| 119 | + " for i in s: \n", |
| 120 | + " if stack and stack[-1] == i.swapcase(): # easy way of changing letter case\n", |
| 121 | + " stack.pop()\n", |
| 122 | + " \n", |
| 123 | + " else:\n", |
| 124 | + " stack.append(i)\n", |
| 125 | + " return \"\".join(stack)\n", |
| 126 | + "\n", |
| 127 | + "#test case\n", |
| 128 | + "s = 'leEeetcode'\n", |
| 129 | + "makeGood(s)" |
| 130 | + ] |
| 131 | + }, |
| 132 | + { |
| 133 | + "cell_type": "markdown", |
| 134 | + "metadata": {}, |
| 135 | + "source": [ |
| 136 | + "---" |
| 137 | + ] |
| 138 | + }, |
| 139 | + { |
| 140 | + "cell_type": "markdown", |
| 141 | + "metadata": {}, |
| 142 | + "source": [ |
| 143 | + "# Question 3: Build an Array With Stack Operations, by Google\n", |
| 144 | + "- Given an array target and an integer n. In each iteration, you will read a number from list = {1,2,3..., n}.\n", |
| 145 | + "- Build the target array using the following operations:\n", |
| 146 | + " - Push: Read a new element from the beginning list, and push it in the array.\n", |
| 147 | + " - Pop: delete the last element of the array.\n", |
| 148 | + " - If the target array is already built, stop reading more elements.\n", |
| 149 | + "- Return the operations to build the target array. You are guaranteed that the answer is unique.\n", |
| 150 | + "- https://leetcode.com/problems/build-an-array-with-stack-operations/" |
| 151 | + ] |
| 152 | + }, |
| 153 | + { |
| 154 | + "cell_type": "code", |
| 155 | + "execution_count": 15, |
| 156 | + "metadata": {}, |
| 157 | + "outputs": [ |
| 158 | + { |
| 159 | + "data": { |
| 160 | + "text/plain": [ |
| 161 | + "['Push', 'Push', 'Pop', 'Push']" |
| 162 | + ] |
| 163 | + }, |
| 164 | + "execution_count": 15, |
| 165 | + "metadata": {}, |
| 166 | + "output_type": "execute_result" |
| 167 | + } |
| 168 | + ], |
| 169 | + "source": [ |
| 170 | + "def buildArray(target,n):\n", |
| 171 | + " stack = []\n", |
| 172 | + " \n", |
| 173 | + " result = []\n", |
| 174 | + " \n", |
| 175 | + " for i in range(1,n+1):\n", |
| 176 | + " if i in target: \n", |
| 177 | + " stack.append(i)\n", |
| 178 | + " result.append('Push')\n", |
| 179 | + " else:\n", |
| 180 | + " stack.append(i)\n", |
| 181 | + " result.append('Push')\n", |
| 182 | + " stack.pop()\n", |
| 183 | + " result.append('Pop')\n", |
| 184 | + " \n", |
| 185 | + " if stack == target:\n", |
| 186 | + " break\n", |
| 187 | + " \n", |
| 188 | + " return result\n", |
| 189 | + "\n", |
| 190 | + "# test case\n", |
| 191 | + "target = [1,3]\n", |
| 192 | + "n = 3\n", |
| 193 | + "buildArray(target,n)" |
| 194 | + ] |
| 195 | + }, |
| 196 | + { |
| 197 | + "cell_type": "markdown", |
| 198 | + "metadata": {}, |
| 199 | + "source": [ |
| 200 | + "----" |
| 201 | + ] |
| 202 | + }, |
| 203 | + { |
| 204 | + "cell_type": "markdown", |
| 205 | + "metadata": {}, |
| 206 | + "source": [ |
| 207 | + "# Question 4: Baseball Game, by Amazon\n", |
| 208 | + "- You are keeping score for a baseball game with strange rules. The game consists of several rounds, where the scores of past rounds may affect future rounds' scores.\n", |
| 209 | + "- At the beginning of the game, you start with an empty record. You are given a list of strings ops, where ops[i] is the ith operation you must apply to the record and is one of the following:\n", |
| 210 | + "- An integer x - Record a new score of x.\n", |
| 211 | + " - \"+\" - Record a new score that is the sum of the previous two scores. It is guaranteed there will always be two previous scores.\n", |
| 212 | + " - \"D\" - Record a new score that is double the previous score. It is guaranteed there will always be a previous score.\n", |
| 213 | + " - \"C\" - Invalidate the previous score, removing it from the record. It is guaranteed there will always be a previous score.\n", |
| 214 | + "- Return the sum of all the scores on the record.\n", |
| 215 | + "- https://leetcode.com/problems/baseball-game/" |
| 216 | + ] |
| 217 | + }, |
| 218 | + { |
| 219 | + "cell_type": "code", |
| 220 | + "execution_count": 16, |
| 221 | + "metadata": {}, |
| 222 | + "outputs": [ |
| 223 | + { |
| 224 | + "data": { |
| 225 | + "text/plain": [ |
| 226 | + "30" |
| 227 | + ] |
| 228 | + }, |
| 229 | + "execution_count": 16, |
| 230 | + "metadata": {}, |
| 231 | + "output_type": "execute_result" |
| 232 | + } |
| 233 | + ], |
| 234 | + "source": [ |
| 235 | + "def calPoints(ops):\n", |
| 236 | + " stack = []\n", |
| 237 | + " for i in ops: \n", |
| 238 | + " if i == \"+\":\n", |
| 239 | + " stack.append(stack[-1]+stack[-2])\n", |
| 240 | + " elif i =='D':\n", |
| 241 | + " stack.append(stack[-1]*2)\n", |
| 242 | + " elif i == 'C':\n", |
| 243 | + " stack.pop()\n", |
| 244 | + " else:\n", |
| 245 | + " stack.append(int(i))\n", |
| 246 | + " return sum(stack)\n", |
| 247 | + "\n", |
| 248 | + "#test case\n", |
| 249 | + "ops = [\"5\",\"2\",\"C\",\"D\",\"+\"]\n", |
| 250 | + "calPoints(ops)" |
| 251 | + ] |
| 252 | + }, |
| 253 | + { |
| 254 | + "cell_type": "markdown", |
| 255 | + "metadata": {}, |
| 256 | + "source": [ |
| 257 | + "----" |
| 258 | + ] |
| 259 | + }, |
| 260 | + { |
| 261 | + "cell_type": "markdown", |
| 262 | + "metadata": {}, |
| 263 | + "source": [ |
| 264 | + "# Question 5: Next Greater Element I, by Amazon and Bloomberg\n", |
| 265 | + "- You are given two integer arrays nums1 and nums2 both of unique elements, where nums1 is a subset of nums2.\n", |
| 266 | + "- Find all the next greater numbers for nums1's elements in the corresponding places of nums2.\n", |
| 267 | + "- The Next Greater Number of a number x in nums1 is the first greater number to its right in nums2. If it does not exist, return -1 for this number.\n", |
| 268 | + "- https://leetcode.com/problems/next-greater-element-i/" |
| 269 | + ] |
| 270 | + }, |
| 271 | + { |
| 272 | + "cell_type": "code", |
| 273 | + "execution_count": 17, |
| 274 | + "metadata": {}, |
| 275 | + "outputs": [ |
| 276 | + { |
| 277 | + "data": { |
| 278 | + "text/plain": [ |
| 279 | + "[-1, 3, -1]" |
| 280 | + ] |
| 281 | + }, |
| 282 | + "execution_count": 17, |
| 283 | + "metadata": {}, |
| 284 | + "output_type": "execute_result" |
| 285 | + } |
| 286 | + ], |
| 287 | + "source": [ |
| 288 | + "# solution 1: brutal force using dictionary\n", |
| 289 | + "def Next_Greater_Element(nums1,nums2):\n", |
| 290 | + " \n", |
| 291 | + " seen = {}\n", |
| 292 | + " \n", |
| 293 | + " for index,value in enumerate(nums2):\n", |
| 294 | + " seen[value]=index\n", |
| 295 | + " \n", |
| 296 | + " \n", |
| 297 | + " result = []\n", |
| 298 | + " \n", |
| 299 | + " for i in nums1:\n", |
| 300 | + " for j in range(seen[i],len(nums2)):\n", |
| 301 | + " if i < nums2[j]:\n", |
| 302 | + " result.append(nums2[j])\n", |
| 303 | + " break\n", |
| 304 | + " else:\n", |
| 305 | + " result.append(-1)\n", |
| 306 | + " return result\n", |
| 307 | + "\n", |
| 308 | + "# test case \n", |
| 309 | + "nums1 = [4,1,2]\n", |
| 310 | + "nums2 = [1,3,4,2]\n", |
| 311 | + "Next_Greater_Element(nums1,nums2)" |
| 312 | + ] |
| 313 | + }, |
| 314 | + { |
| 315 | + "cell_type": "code", |
| 316 | + "execution_count": 1, |
| 317 | + "metadata": {}, |
| 318 | + "outputs": [ |
| 319 | + { |
| 320 | + "data": { |
| 321 | + "text/plain": [ |
| 322 | + "[-1, 3, -1]" |
| 323 | + ] |
| 324 | + }, |
| 325 | + "execution_count": 1, |
| 326 | + "metadata": {}, |
| 327 | + "output_type": "execute_result" |
| 328 | + } |
| 329 | + ], |
| 330 | + "source": [ |
| 331 | + "#solution 2: stack \n", |
| 332 | + "def Next_Greater_Element(nums1,nums2):\n", |
| 333 | + " \n", |
| 334 | + " stack = []\n", |
| 335 | + " \n", |
| 336 | + " ans = {}\n", |
| 337 | + " \n", |
| 338 | + " for num in nums2:\n", |
| 339 | + "\n", |
| 340 | + " while stack and stack[-1] < num:\n", |
| 341 | + " \n", |
| 342 | + " anum = stack.pop()\n", |
| 343 | + " \n", |
| 344 | + " ans[anum] = num\n", |
| 345 | + "\n", |
| 346 | + " stack.append(num)\n", |
| 347 | + "\n", |
| 348 | + " return([ans.get(i,-1) for i in nums1]) # get i's value or return -1 if it does not exist\n", |
| 349 | + "\n", |
| 350 | + "# test case \n", |
| 351 | + "nums1 = [4,1,2]\n", |
| 352 | + "nums2 = [1,3,4,2]\n", |
| 353 | + "Next_Greater_Element(nums1,nums2)" |
| 354 | + ] |
| 355 | + }, |
| 356 | + { |
| 357 | + "cell_type": "markdown", |
| 358 | + "metadata": {}, |
| 359 | + "source": [ |
| 360 | + "----" |
| 361 | + ] |
| 362 | + } |
| 363 | + ], |
| 364 | + "metadata": { |
| 365 | + "kernelspec": { |
| 366 | + "display_name": "Python 3", |
| 367 | + "language": "python", |
| 368 | + "name": "python3" |
| 369 | + }, |
| 370 | + "language_info": { |
| 371 | + "codemirror_mode": { |
| 372 | + "name": "ipython", |
| 373 | + "version": 3 |
| 374 | + }, |
| 375 | + "file_extension": ".py", |
| 376 | + "mimetype": "text/x-python", |
| 377 | + "name": "python", |
| 378 | + "nbconvert_exporter": "python", |
| 379 | + "pygments_lexer": "ipython3", |
| 380 | + "version": "3.7.4" |
| 381 | + } |
| 382 | + }, |
| 383 | + "nbformat": 4, |
| 384 | + "nbformat_minor": 2 |
| 385 | +} |
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