LeetCode -- Next Permutation

LeetCode -- Next Permutation

Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.

If such arrangement is not possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order ).

The replacement must be in-place, do not allocate extra memory.

Here are some examples. Inputs are in the left-hand column and its corresponding outputs are in the right-hand column.
1,2,3→1,3,2
3,2,1→1,2,3
1,1,5→1,5,1

Original question link: https://oj.leetcode.com/problems/next-permutation/

Question: implement the next arrangement, which rearranges the given array in lexicographically greater order than the next one.

Idea: The next arrangement is actually a big and closest arrangement than the current one. The specific method is: in the array, from the back to the back, find the place where the last ascending order, exchange the pre-and post-value, and reverse the subsequent Original Order to the ascending order.

public void nextPermutation(int[] num) {int len = num.length, i = 0, j = 0;for (i = len - 2; i >= 0; i--) {if (num[i] >= num[i + 1])continue;for (j = len - 1; j > i; j--) {if (num[j] > num[i])break;}break;}if (i >= 0) {int temp = num[i];num[i] = num[j];num[j] = temp;}int end = len - 1;int start = i + 1;while (start < end) {int temp = num[start];num[start] = num[end];num[end] = temp;start++;end--;}}