leetcode 下一个排列

public String getPermutation(int n, int k) {
        int[] nums = new int[n];
        for(int i = 0;i < n;i++){
            nums[i] = i+1;
        }
        int nTemp = n;
        int kTemp = k;
        for(int i = 0;i<n-1;i++){
            int mod = kTemp % cal(nTemp-1);
            int quotient = kTemp /cal(nTemp-1);
            if(mod == 0){
                swap(nums,i,i+quotient-1);
                kTemp = cal(nTemp-1);
            }else{
                swap(nums,i,i+quotient);
                kTemp = mod;
            }
            insertsort(nums,i+1,n-1);
            nTemp--;
        }
        StringBuilder str = new StringBuilder();
        for (int i = 0; i < n; i++) {
            str.append(nums[i]);
        }
        return new String(str);
    }
    private void swap(int[]nums,int i,int j){
        int temp = nums[i];
        nums[i] = nums[j];
        nums[j] = temp;
    }
    private int cal(int n){
        int res = 1;
        for(int i = 1;i<=n;i++){
            res*=i;
        }
        return res;
    }
    private void insertsort(int[]nums,int start,int end){
        int j = 0;
        for(int i = start+1;i<=end;i++){
            int key = nums[i];
            for(j = i-1;j>=start;j--){
                if(nums[j]>key){
                    nums[j+1] = nums[j];
                }else{
                    break;
                }
                
            }
            nums[j+1] = key;
        }
    }