AyushSoni86 · AyushSoni86 · Dec 27, 2022 · Dec 27, 2022
diff --git a/DS_04_Array_and_Questions/Part_1/part1.txt b/DS_04_Array_and_Questions/Part_1/part1.txt
diff --git a/DS_04_Array_and_Questions/Part_2/part2.txt b/DS_04_Array_and_Questions/Part_2/part2.txt
diff --git a/DS_04_Array_and_Questions/array.txt b/DS_04_Array_and_Questions/array.txt
diff --git a/DS_04_Array_and_Strings/Arrays_and_Questions/MajorityElement.java b/DS_04_Array_and_Strings/Arrays_and_Questions/MajorityElement.java
@@ -0,0 +1,46 @@
+package DS_04_Array_and_Strings.Arrays_and_Questions;
+
+public class MajorityElement {
+
+    // gfg link - https://practice.geeksforgeeks.org/problems/majority-element-1587115620/1
+    // gfg solution
+    static int majorityElement(int arr[], int size){
+        int ansIndex = 0;
+        int count = 1;
+        for(int i = 1 ; i < arr.length ; i++){
+            if(arr[i] == arr[ansIndex]){
+                count ++;
+            }else{
+                count--;
+            }
+            if(count == 0){
+                count = 1;
+                ansIndex = i;
+            }
+        }
+
+        int major = arr[ansIndex];
+        int ans = 0;
+        for(int i = 0 ; i < arr.length ; i++){
+            if(arr[i] == major) ans++;
+        }
+
+        return ans > size/2 ? major: -1;
+    }
+
+    // leetcode link - https://leetcode.com/problems/majority-element/
+    // leetcode solution
+    public int majorityElement(int[] arr) {
+        int ansIndex = 0, cnt = 1;      
+        for(int i = 1 ; i < arr.length ; i++){
+            if(arr[i]== arr[ansIndex]) cnt++;
+            else cnt--;
+            if(cnt == 0) {
+                cnt = 1;
+                ansIndex = i;
+            }
+        }        
+        return  arr[ansIndex];
+    }
+
+}
diff --git a/DS_04_Array_and_Strings/Arrays_and_Questions/Max_Till_i.java b/DS_04_Array_and_Strings/Arrays_and_Questions/Max_Till_i.java
@@ -0,0 +1,14 @@
+package DS_04_Array_and_Strings.Arrays_and_Questions;
+
+import java.util.Arrays;
+
+public class Max_Till_i {
+    public static void main(String[] args) {
+        int arr[] = { 1, 0, 5, 4, 6, 8 };
+
+        for (int i = 1; i < arr.length; i++) {
+           arr[i] =  Math.max(arr[i-1], arr[i]);
+        }
+        System.out.println(Arrays.toString(arr));
+    }
+}
diff --git a/DS_04_Array_and_Strings/Arrays_and_Questions/MaximunSumSubArray.java b/DS_04_Array_and_Strings/Arrays_and_Questions/MaximunSumSubArray.java
@@ -0,0 +1,45 @@
+package DS_04_Array_and_Strings.Arrays_and_Questions;
+
+public class MaximunSumSubArray {
+
+    // kadane's algorithm 
+    static int maxSumSubArray(int[] arr){
+        int maxSum = 0;
+        int currentSum = 0;
+        for(int i = 0 ; i < arr.length ; i++){
+            currentSum = currentSum + arr[i];
+            if(currentSum > maxSum){
+                maxSum = currentSum;
+            }
+            if(currentSum < 0){
+                currentSum = 0;
+            }
+        }
+        return maxSum;
+
+    }
+
+    // gfg link : https://practice.geeksforgeeks.org/problems/kadanes-algorithm-1587115620/1 
+    long maxSubarraySum(int arr[], int n){
+        long maxSum = 0;
+        long currentSum = 0;
+        for(int i = 0 ; i < arr.length ; i++){
+            currentSum = currentSum + arr[i];
+            if(currentSum > maxSum){
+                maxSum = currentSum;
+            }
+            if(currentSum < 0){
+                currentSum = 0;
+            }
+        }
+        return maxSum > 0 ? maxSum : findMax(arr);
+    }
+
+    long findMax(int[] arr){
+        long max = arr[0];
+        for(int i = 0 ; i < arr.length ; i++){
+            if(arr[i] > max) max = arr[i];
+        }
+        return max;
+    }
+}
diff --git a/DS_04_Array_and_Strings/Arrays_and_Questions/MultiDimensionalArray/SpiralPrint.java b/DS_04_Array_and_Strings/Arrays_and_Questions/MultiDimensionalArray/SpiralPrint.java
@@ -0,0 +1,54 @@
+package DS_04_Array_and_Strings.Arrays_and_Questions.MultiDimensionalArray;
+
+public class SpiralPrint {
+    public static void main(String[] args) {
+        int[][] arr = {
+                { 1, 2, 3 },
+                { 4, 5, 6 },
+                { 7, 8, 9 }
+        };
+        spiralPrint(arr);
+    }
+
+    static void spiralPrint(int[][] arr) {
+        int row = arr.length;
+        int col = arr[0].length;
+        int total = row * col;
+        int count = 0;
+
+        int startCol = 0;
+        int startRow = 0;
+        int endCol = col - 1;
+        int endRow = row - 1;
+
+        while (count < total) {
+            // print first row
+            for (int i = startCol; i <= endCol; i++) {
+                System.out.print(arr[startRow][i] + " ");
+                count++;
+            }
+            startRow++;
+
+            // print last column
+            for (int i = startRow; i <= endRow; i++) {
+                System.out.print(arr[i][endCol] + " ");
+                count++;
+            }
+            endCol--;
+
+            // print last row
+            for (int i = endCol; i >= startCol; i--) {
+                System.out.print(arr[endRow][i] + " ");
+                count++;
+            }
+            endRow--;
+            // print first column
+            for (int i = endRow; i >= startRow; i--) {
+                System.out.print(arr[i][startCol] + " ");
+                count++;
+            }
+            startCol++;
+        }
+
+    }
+}
diff --git a/DS_04_Array_and_Strings/Arrays_and_Questions/RainwaterTrapping.java b/DS_04_Array_and_Strings/Arrays_and_Questions/RainwaterTrapping.java
@@ -0,0 +1,5 @@
+package DS_04_Array_and_Strings.Arrays_and_Questions;
+
+public class RainwaterTrapping {
+
+}
diff --git a/DS_04_Array_and_Strings/Arrays_and_Questions/StockBuyAndSell1.java b/DS_04_Array_and_Strings/Arrays_and_Questions/StockBuyAndSell1.java
@@ -0,0 +1,19 @@
+package DS_04_Array_and_Strings.Arrays_and_Questions;
+
+public class StockBuyAndSell1 {
+    // Question 3 : Stock Buy and Sell (part - 1 : one stock at a time)
+    // leetcode link :
+    // https://leetcode.com/problems/best-time-to-buy-and-sell-stock/
+
+    public int maxProfit(int[] arr) {
+        int max = 0;
+        int minSoFar = arr[0];
+        for (int i = 0; i < arr.length; i++) {
+            minSoFar = Math.min(minSoFar, arr[i]);
+            int profit = arr[i] - minSoFar;
+            max = Math.max(max, profit);
+        }
+        return max;
+    }
+
+}
diff --git a/DS_04_Array_and_Strings/Arrays_and_Questions/StockBuyAndSell2.java b/DS_04_Array_and_Strings/Arrays_and_Questions/StockBuyAndSell2.java
@@ -0,0 +1,18 @@
+package DS_04_Array_and_Strings.Arrays_and_Questions;
+
+public class StockBuyAndSell2 {
+    // Question 4 : Stock Buy and Sell (part - 2 : buy any number of stock)
+    // leetcode link :
+    // https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/
+
+    public int maxProfit(int[] arr) {
+        int profit = 0;
+        for (int i = 1; i < arr.length; i++) {
+            if (arr[i] > arr[i - 1]) {
+                profit = profit + arr[i] - arr[i - 1];
+            }
+        }
+        return profit;
+    }
+
+}
diff --git a/DS_04_Array_and_Strings/Arrays_and_Questions/SumOfAllSubArrays.java b/DS_04_Array_and_Strings/Arrays_and_Questions/SumOfAllSubArrays.java
@@ -0,0 +1,18 @@
+package DS_04_Array_and_Strings.Arrays_and_Questions;
+
+public class SumOfAllSubArrays {
+    public static void main(String[] args) {
+        int[] arr = { 1, 2, 0, 7, 2 };
+        sum(arr);
+    }
+
+    static void sum(int[] arr) {
+        for (int i = 0; i < arr.length; i++) {
+            int ans = 0;
+            for (int j = i; j < arr.length; j++) {
+                ans = ans + arr[j];
+                System.out.println(ans); 
+            }
+        }
+    }
+}
diff --git a/DS_04_Array_and_Strings/Arrays_and_Questions/array.txt b/DS_04_Array_and_Strings/Arrays_and_Questions/array.txt
@@ -0,0 +1,10 @@
+Majority Elements
+Maximum Sum Subarray
+Stock Buy And Sell - 1
+Stock Buy And Sell - 2
+Rainwater trapping problems
+
+
+maximum till i
+
+sum of all subarrays