LeetCode-in-Rust
560. Subarray Sum Equals K
Medium
Given an array of integers nums and an integer k, return the total number of subarrays whose sum equals to k.
A subarray is a contiguous non-empty sequence of elements within an array.
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
Solution
use std::collections::HashMap;
impl Solution {
pub fn subarray_sum(nums: Vec<i32>, k: i32) -> i32 {
let mut temp_sum = 0;
let mut ret = 0;
let mut sum_count: HashMap<i32, i32> = HashMap::new();
sum_count.insert(0, 1);
for &num in nums.iter() {
temp_sum += num;
if let Some(&count) = sum_count.get(&(temp_sum - k)) {
ret += count;
}
let entry = sum_count.entry(temp_sum).or_insert(0);
*entry += 1;
}
ret
}
}