31. Next Permutation

Runtime    0 ms
Beats      100%


Memory     41.6 MB
Beats      98.42%


class Solution {

    public static void reverse(int a[],int i){
        int j=i,k=a.length-1;
        while(j<k){
            swap(a,j,k);
            j++;k--;
        }
    }

    public static void swap(int a[],int i,int j){
        int temp=a[i];
        a[i]=a[j]; 
        a[j]=temp;
    }


    public void nextPermutation(int[] nums) {
        int index=-1,n=nums.length,i=0;

        for( i=n-2;i>=0;i--){
            if(nums[i]<nums[i+1]){
                index=i;
                break;
            }
        }

        if(index == -1){
            reverse(nums,0);
        }else{
            for( i=n-1;i>=index;i--){
            if(nums[i]>nums[index]){
                swap(nums,i,index);
                break;
            }
        }

        reverse(nums,index+1);
        }

        

    }
}