题目

Given a char array representing tasks CPU need to do. It contains capital letters A to Z where different letters represent different tasks.Tasks could be done without original order. Each task could be done in one interval. For each interval, CPU could finish one task or just be idle.

However, there is a non-negative cooling interval n that means between two same tasks, there must be at least n intervals that CPU are doing different tasks or just be idle.

You need to return the least number of intervals the CPU will take to finish all the given tasks.

Example 1:

Input: tasks = ["A","A","A","B","B","B"], n = 2
Output: 8


Explanation: A -> B -> idle -> A -> B -> idle -> A -> B.

Note: The number of tasks is in the range [1, 10000]. The integer n is in the range [0, 100].

数学原理

 gap1 gap2 gap3
|    |    |    |
AXXX AXXX AXXX A


 gap1 gap2 gap3
|    |    |    |
AXXX AXXX AXXX A

ABXX ABXX ABXX A
ABEX ABEX ABFX A
...
...
ABEF ABEG ABFX A


(MaxFreq - 1) * (n + 1) + 1

填满以后：
ABEF ABEG ABFG A



ABEFHIK ABEGHI ABFGHJ A


ABXX ABXX ABXX AB


(MaxFreq - 1) * (n + 1) + NumOfMaxFreqTask

ABCD ABCD ABCD


ABC ABC ABC


代码

class Solution {
public int leastInterval(char[] tasks, int n) {
int[] freq = new int[26];
for (int i = 0; i < tasks.length; i++) {
}
Arrays.sort(freq);
int cur = freq.length - 1;
int maxSize = freq[cur], num = 0;
while (cur >= 0 && freq[cur] == maxSize) {
num++; cur--;
}
int standard = (maxSize - 1) * (n + 1) + num;