681. Next Closest Time

Given a time represented in the format "HH:MM", form the next closest time by reusing the current digits. There is no limit on how many times a digit can be reused.

You may assume the given input string is always valid. For example, "01:34", "12:09" are all valid. "1:34", "12:9" are all invalid.

Example 1:

Input: time = "19:34"
Output: "19:39"
Explanation: The next closest time choosing from digits 1, 9, 3, 4, is 19:39, which occurs 5 minutes later.
It is not 19:33, because this occurs 23 hours and 59 minutes later.

Example 2:

Input: time = "23:59"
Output: "22:22"
Explanation: The next closest time choosing from digits 2, 3, 5, 9, is 22:22.
It may be assumed that the returned time is next day's time since it is smaller than the input time numerically.

Constraints:

• time.length == 5
• time is a valid time in the form "HH:MM".
• 0 <= HH < 24
• 0 <= MM < 60

Solution:

感觉这个方法不粗, 得学学 TreeSet 是啥了

class Solution {
    public String nextClosestTime(String time) {
        TreeSet<Character> set = new TreeSet<>();
        for(int i = 0; i<5; i++) {
            if(i != 2)
                set.add(time.charAt(i));
        }
        char[] nextTime = time.toCharArray();
        for(int i = 4; i>=0; i--) {
            if(i == 2) continue;
            Character nextHigherNum = set.higher(nextTime[i]);
            if(nextHigherNum != null && isValid(nextTime, nextHigherNum, i)) {
                nextTime[i] = nextHigherNum;
                break;
            }
            nextTime[i] = set.first();
        }
        return new String(nextTime);
    }

    private boolean isValid(char[] nextTime, char num, int placeHolder) {
        if(placeHolder == 3 && num > '5')
            return false;
        if(placeHolder == 1 && num > '3' && nextTime[0] == '2')
            return false;
        if(placeHolder == 0 && num > '2')
            return false;
        return true;
    }
}

似曾相识 嗯... 外包 USC 有个和这个类似的