【LeetCode】1013. Pairs of Songs With Total Durations Divisible by 60（取模）

【LeetCode】1013. Pairs of Songs With Total Durations Divisible by 60（取模）

题目

In a list of songs, the i-th song has a duration of time[i] seconds.

Return the number of pairs of songs for which their total duration in seconds is divisible by 60. Formally, we want the number of indices $i<j$ with $(time[i]+time[j])\%60==0$.

Example 1:

Input: [30,20,150,100,40]
Output: 3
Explanation: Three pairs have a total duration divisible by 60:
(time[0] = 30, time[2] = 150): total duration 180
(time[1] = 20, time[3] = 100): total duration 120
(time[1] = 20, time[4] = 40): total duration 60

Example 2:

Input: [60,60,60]
Output: 3
Explanation: All three pairs have a total duration of 120, which is divisible by 60.

Note:

1 <= time.length <= 60000
1 <= time[i] <= 500

思路

这题其实蛮简单的，注意的地方有两个：
（1）$(a+b)\%60=(a\%60+b\%60)\%60$。因此，可以在遍历给定数组的时候，可以直接将每个数向60取模；
（2）将数据离散化。

代码

class Solution {
public:
    int numPairsDivisibleBy60(vector& time) {
        int i, j, k, s, ans;
        mapm;
        m.clear();

        ans = 0;
        for(i=0; i