974. Subarray Sums Divisible by K

[Tcdian]

974. Subarray Sums Divisible by K

给定一个整数数组 A，返回其中元素之和可被 K 整除的（连续、非空）子数组的数目。

Example

Input: A = [4,5,0,-2,-3,1], K = 5
Output: 7
Explanation: There are 7 subarrays with a sum divisible by K = 5:
[4, 5, 0, -2, -3, 1], [5], [5, 0], [5, 0, -2, -3], [0], [0, -2, -3], [-2, -3]

Note

• 1 <= A.length <= 30000
• -10000 <= A[i] <= 10000
• 2 <= K <= 10000

[Tcdian]

Solution

• JavaScript Solution

/**
 * @param {number[]} A
 * @param {number} K
 * @return {number}
 */
var subarraysDivByK = function(A, K) {
    let prefix = 0;
    const cache = new Map([[prefix, 1]]);
    let result = 0;
    for (let i = 0; i < A.length; i++) {
        prefix += A[i];
        while(prefix < 0) {
            prefix += K;
        }
        if (cache.has(prefix % K)) {
            result += cache.get(prefix % K);
        }
        cache.set(prefix % K, (cache.get(prefix % K) || 0) + 1);
    }
    return result;
};

• TypeScript Solution

var subarraysDivByK = function(A: number[], K: number): number {
    let prefix = 0;
    const cache = new Map([[prefix, 1]]);
    let result = 0;
    for (let i = 0; i < A.length; i++) {
        prefix += A[i];
        while(prefix < 0) {
            prefix += K;
        }
        if (cache.has(prefix % K)) {
            result += cache.get(prefix % K) as number;
        }
        cache.set(prefix % K, (cache.get(prefix % K) || 0) + 1);
    }
    return result;
};