949. Largest Time for Given Digits

Problem Link

Description

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Given an array arr of 4 digits, find the latest 24-hour time that can be made using each digit exactly once.

24-hour times are formatted as "HH:MM", where HH is between 00 and 23, and MM is between 00 and 59. The earliest 24-hour time is 00:00, and the latest is 23:59.

Return the latest 24-hour time in "HH:MM" format. If no valid time can be made, return an empty string.

 

Example 1:

Input: arr = [1,2,3,4]
Output: "23:41"
Explanation: The valid 24-hour times are "12:34", "12:43", "13:24", "13:42", "14:23", "14:32", "21:34", "21:43", "23:14", and "23:41". Of these times, "23:41" is the latest.

Example 2:

Input: arr = [5,5,5,5]
Output: ""
Explanation: There are no valid 24-hour times as "55:55" is not valid.

 

Constraints:

• arr.length == 4
• 0 <= arr[i] <= 9

Solution

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Python3

class Solution:
    def largestTimeFromDigits(self, arr: List[int]) -> str:
        for perm in permutations(sorted(arr, reverse = 1)):
            if perm[0] * 10 + perm[1] < 24 and perm[2] < 6:
                return f"{perm[0]}{perm[1]}:{perm[2]}{perm[3]}"
        
        return ""

C++

class Solution {
public:
	string largestTimeFromDigits(vector<int>& A) {
		string ans = "";
		sort(A.begin(),A.end());
		do
		{
			if((A[0]==2 && A[1]<=3 || A[0]<2) && A[2]<=5)
			{
				string temp = to_string(A[0])+to_string(A[1])+":"
					+to_string(A[2])+to_string(A[3]);
				if(temp > ans) ans = temp;
			}       
		}while(next_permutation(A.begin(),A.end()));
		return ans;
	}
};