1055. Pairs Of Songs With Total Durations Divisible By 60¶

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1055. Pairs of Songs With Total Durations Divisible by 60

Medium

You are given a list of songs where the ith 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 such that i < j with (time[i] + time[j]) % 60 == 0.

Example 1:

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

Constraints:

• 1 <= time.length <= 6 * 104
• 1 <= time[i] <= 500

Solution¶

class Solution {
    public int numPairsDivisibleBy60(int[] time) {
        int n = time.length;
        int freq[] = new int[1001];
        int count = 0;
        for (int i = 0; i < n; i++) {
            int current = time[i];
            for (int j = 60; j <= 1000; j += 60) if (j - current > 0) count += freq[j - current];
            freq[current]++;
        }
        return count;
    }
}

Complexity Analysis¶

• Time Complexity: O(?)
• Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here