Longest palindromic subsequence in JAVA

Java/Dynamic_Programming/LongestCommonSubsequence.java

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+package Java.Dynamic_Programming;
+import java.util.*;
+public class LongestCommonSubsequence {
+
+    public static void main(String[] args) {
+        Scanner scan = new Scanner(System.in);
+
+        String a = scan.next();
+        String b = scan.next();
+
+        int m = a.length();
+        int n = b.length();
+
+        LongestCommonSubsequence lcs = new LongestCommonSubsequence();
+        lcs.getLCS(a,b,m,n);
+
+        scan.close();
+    }
+    private void getLCS(String a, String b, int m, int n) {
+        int dp[][] = new int[m+1][n+1];
+        for(int i=0;i<=m;i++){
+            for(int j=0;j<=n;j++){
+                if(i==0 || j==0){
+                    dp[i][j] = 0;
+                }
+                else if(a.charAt(i-1) == b.charAt(j-1)){
+                    dp[i][j] = 1 + dp[i-1][j-1];
+                }
+                else{
+                    dp[i][j] = Math.max(dp[i-1][j], dp[i][j-1]);
+                }
+            }
+        }
+        int len = dp[m][n];
+
+        String res = "";
+        int i = m;
+        int j = n;
+        while (i > 0 && j > 0) {
+            if (a.charAt(i - 1) == b.charAt(j - 1)) {
+                res += Character.toString(a.charAt(i - 1));
+                i--;
+                j--;
+            }
+
+            else if (dp[i - 1][j] > dp[i][j - 1])
+                i--;
+            else
+                j--;
+        }
+        System.out.println("Length of lCS is : "+ len);
+        System.out.println("LCS string is : "+ new StringBuilder(res).reverse().toString());
+    }
+}

Java/Dynamic_Programming/LongestPalindromicSubsequence.java

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+package Java.Dynamic_Programming;
+import java.util.*;
+public class LongestPalindromicSubsequence {
+    public static void main(String[] args) {
+        Scanner scan = new Scanner(System.in);
+
+        String a = scan.next();
+        int m = a.length();
+
+        LongestPalindromicSubsequence lps = new LongestPalindromicSubsequence();
+        lps.getLPS(a,m);
+
+        scan.close();
+    }
+    private void getLPS(String a,int m) {
+        String b = new StringBuilder(a).reverse().toString();
+
+        int dp[][] = new int[m+1][m+1];
+        for(int i=0;i<=m;i++){
+            for(int j=0;j<=m;j++){
+                if(i==0 || j==0){
+                    dp[i][j] = 0;
+                }
+                else if(a.charAt(i-1) == b.charAt(j-1)){
+                    dp[i][j] = 1 + dp[i-1][j-1];
+                }
+                else{
+                    dp[i][j] = Math.max(dp[i-1][j], dp[i][j-1]);
+                }
+            }
+        }
+        int len = dp[m][m];
+
+        String res = "";
+        int i = m;
+        int j = m;
+        while (i > 0 && j > 0) {
+            if (a.charAt(i - 1) == b.charAt(j - 1)) {
+                res += Character.toString(a.charAt(i - 1));
+                i--;
+                j--;
+            }
+
+            else if (dp[i - 1][j] > dp[i][j - 1])
+                i--;
+            else
+                j--;
+        }
+        System.out.println("Length of LPS is : "+ len);
+        System.out.println("LPS string is : "+ new StringBuilder(res).reverse().toString());
+    }
+}

Java/Sorting/QuickSort.java

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+/**  
+ * 
+ *   1. Quick Sort is an inplace sorting algorithm based on Divide and Conquer Approach.
+ *   2. First a pivot element is choosen and partitions are made around the choosen pivot.
+ *   3. Selection of pivot element decides the time complexity of algorithm.
+ * 
+ */
+
+package Java.Sorting;
+
+import java.util.*;
+public class QuickSort {
+    static void swap(int[] arr, int i, int j)
+    {
+        int temp = arr[i];
+        arr[i] = arr[j];
+        arr[j] = temp;
+    }
+
+    static int partition(int[] arr, int low, int high)
+    {
+        int pivot = arr[high];
+        int i = (low - 1);
+
+        for (int j = low; j <= high - 1; j++) {
+            if (arr[j] < pivot) {
+                i++;
+                swap(arr, i, j);
+            }
+        }
+        swap(arr, i + 1, high);
+        return (i + 1);
+    }
+
+    static void quickSort(int[] arr, int low, int high)
+    {
+        if (low < high) {
+            int pi = partition(arr, low, high);
+            quickSort(arr, low, pi - 1);
+            quickSort(arr, pi + 1, high);
+        }
+    }
+
+    static void printArray(int[] arr, int size)
+    {
+        for (int i = 0; i < size; i++)
+            System.out.print(arr[i] + " ");
+
+        System.out.println();
+    }
+
+    public static void main(String[] args)
+    {
+        Scanner scan = new Scanner(System.in);
+        int n = scan.nextInt();
+
+        int[] arr = new int[n];
+        for(int i=0;i<n;i++){
+            arr[i] = scan.nextInt();
+        }
+
+        System.out.println("Array before sorting");
+        printArray(arr, n);
+        System.out.println();
+
+        quickSort(arr, 0, n - 1);
+
+        System.out.println("Array after sorting ");
+        printArray(arr, n);
+        System.out.println();
+
+        scan.close();
+    }
+}
+
+
+// Contributor : Rishabh Srivastava 
+// Github Link : https://github.com/RishabhSrivastava1423/