Merge pull request #206 from RAshid602/testing-permutation

Testing permutation

Author: SarthakKeshari

Number Theory/nextpermutation.java

@@ -0,0 +1,72 @@
+//Implement next permutation, which rearranges numbers into the lexicographically 
+//next greater permutation of numbers.
+
+import java.util.Scanner;
+
+public class nextpermutation {
+
+    //This function is used to take input and store in array
+    public static int[] input() {
+        System.out.println("Enter the size array:");
+        Scanner sc = new Scanner(System.in);
+        int n;
+        n = sc.nextInt();
+        int a[] = new int[n];
+        System.out.println("Enter the  array: ");
+        for (int i = 0; i < n; i++) {
+            a[i] = sc.nextInt();
+        }
+        return a;
+
+    }
+//This function is used to print the desired output
+    public static void print(int a[]) {
+        System.out.println("The array: ");
+        int n = a.length;
+        for (int i = 0; i < n; i++) {
+            System.out.print(a[i] + " ");
+        }
+        System.out.println();
+    }
+    public static int[] nextPermutation(int[] nums) {
+        int i = nums.length - 2;
+        while (i >= 0 && nums[i + 1] <= nums[i]) {
+            i--;
+        }
+        //  sort from i + 1 or reverse it as you will get decreasing order from i + 1
+        if (i >= 0) {
+            int j = nums.length - 1;
+            while (nums[j] <= nums[i]) {
+                j--;
+            }
+            swap(nums, i, j);
+        }
+        reverse(nums, i + 1);
+        return nums;
+    }
+    
+    private static void reverse(int[] nums, int start) {
+        int i = start, j = nums.length - 1;
+        while (i < j) {
+            swap(nums, i, j);
+            i++;
+            j--;
+        }
+    }
+  //Actual function to swapp
+    private static void swap(int[] nums, int i, int j) {
+        int temp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = temp;
+    }
+
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        
+
+            int a[] = input();
+           int b[]= nextPermutation(a);
+           print(b);
+        
+    }
+}