949. Largest Time for Given Digits

Given an array of 4 digits, return the largest 24 hour time that can be made.

The smallest 24 hour time is 00:00, and the largest is 23:59.  Starting from 00:00, a time is larger if more time has elapsed since midnight.

Return the answer as a string of length 5.  If no valid time can be made, return an empty string.

Example 1:

Input: [1,2,3,4]
Output: "23:41"

Example 2:

Input: [5,5,5,5]
Output: ""

Note:

1. A.length == 4
2. 0 <= A[i] <= 9

class Solution {
     public String largestTimeFromDigits(int[] A) {
            String ans = "";
            for (int i = 0; i < 4; ++i) {
                for (int j = 0; j < 4; ++j) {
                    for (int k = 0; k < 4; ++k) {
                        for(int l = 0; l < 4; l++) {
                            if (i == j || i == k || i == l || j == k || j == l || k == l) continue; // avoid duplicate among i, j & k.
                        String h = "" + A[i] + A[j], m = "" + A[k] + A[l], t = h + ":" + m; // hour, minutes, & time.
                        if (h.compareTo("24") < 0 && m.compareTo("60") < 0 && ans.compareTo(t) < 0) ans = t; // hour < 24; minute < 60; update result.
                        }
                        
                    }
                }
            }
            return ans;
        }
}

垃圾题。。permutation数组里的四位，符合条件且更大就update