LeetCode-in-Dart
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
class Solution {
int subarraySum(List<int> nums, int k) {
int tempSum = 0;
int ret = 0;
Map<int, int> sumCount = {0: 1};
for (int i in nums) {
tempSum += i;
if (sumCount.containsKey(tempSum - k)) {
ret += sumCount[tempSum - k]!;
}
if (sumCount.containsKey(tempSum)) {
sumCount[tempSum] = sumCount[tempSum]! + 1;
} else {
sumCount[tempSum] = 1;
}
}
return ret;
}
}