Add 31_Next_Permutation.java

Author: Sean Prashad

Arrays/31_Next_Permutation.java

@@ -0,0 +1,44 @@
+class Solution {
+ public void nextPermutation(int[] nums) {
+ if (nums == null || nums.length == 0) {
+ return;
+ }
+
+ int n = nums.length - 1, idx = -1;
+
+ for (int i = n - 1; i >= 0; i--) {
+ if (nums[i] < nums[i + 1]) {
+ idx = i;
+ break;
+ }
+ }
+
+ if (idx == -1) {
+ reverseArray(nums, 0, n);
+ return;
+ }
+
+ for (int i = n; i >= 0; i--) {
+ if (nums[i] > nums[idx]) {
+ swap(nums, i, idx);
+ break;
+ }
+ }
+
+ reverseArray(nums, idx + 1, n);
+ }
+
+ private void reverseArray(int[] nums, int start, int end) {
+ while (start < end) {
+ swap(nums, start, end);
+ ++start;
+ --end;
+ }
+ }
+
+ private void swap(int[] nums, int i, int j) {
+ int temp = nums[i];
+ nums[i] = nums[j];
+ nums[j] = temp;
+ }
+}