31. Next Permutation

 

Example 1:

Input: nums = [1,2,3]
Output: [1,3,2]

Example 2:

Input: nums = [3,2,1]
Output: [1,2,3] 

class Solution {

public void nextPermutation(int[] nums) {

int pivot = -1;

int n = nums.length;

for(int i = n-2;i >=0 ;i--){

if(nums[i] < nums[i+1]){

pivot = i;

break;

}

}

if(pivot == -1){

reverse(nums,0,n-1);

return;

}

for(int i = n-1;i > pivot;i--){

if(nums[pivot] < nums[i]){

swap(nums,pivot,i);

break;

}

}

reverse(nums,pivot+1,n-1);

}

public void reverse(int nums[], int start,int end){

while(start < end){

swap(nums,start++,end--);

}

}

public void swap(int nums[], int i, int j){

int temp = nums[i];

nums[i] = nums[j];

nums[j] = temp;

}

}