# ---
# title: 949. Largest Time for Given Digits
# id: problem949
# author: Tian Jun
# date: 2020-10-31
# difficulty: Medium
# categories: Math
# link: <https://leetcode.com/problems/largest-time-for-given-digits/description/>
# hidden: true
# ---
# 
# 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: A = [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: A = [5,5,5,5]
#     Output: ""
#     Explanation:  There are no valid 24-hour times as "55:55" is not valid.
#     
# 
# **Example 3:**
# 
#     
#     
#     Input: A = [0,0,0,0]
#     Output: "00:00"
#     
# 
# **Example 4:**
# 
#     
#     
#     Input: A = [0,0,1,0]
#     Output: "10:00"
#     
# 
# 
# 
# **Constraints:**
# 
#   * `arr.length == 4`
#   * `0 <= arr[i] <= 9`
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
