README.md

560. Subarray Sum Equals K

Given an array of integers nums and an integer k, return the total number of continuous subarrays whose sum equals to k.

Example 1:

Input: nums = [1,1,1], k = 2
Output: 2

Example 2:

Input: nums = [1,2,3], k = 3
Output: 2

Constraints:

• 1 <= nums.length <= 2 * 104
• -1000 <= nums[i] <= 1000
• -107 <= k <= 107

Solutions (Rust)

1. HashMap

use std::collections::HashMap;

impl Solution {
    pub fn subarray_sum(nums: Vec<i32>, k: i32) -> i32 {
        let mut count = vec![(0, 1)].into_iter().collect::<HashMap<_, _>>();
        let mut sum = 0;
        let mut ret = 0;

        for num in nums {
            sum += num;
            ret += count.get(&(sum - k)).unwrap_or(&0);
            *count.entry(sum).or_insert(0) += 1;
        }

        ret
    }
}