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
public class Solution {
public int SubarraySum(int[] nums, int k) {
var map = new Dictionary<int,int>();
map.Add(0,1);
int sum = 0;
int res = 0;
for(int i=0;i<nums.Length;i++){
sum += nums[i];
int count = 0;
map.TryGetValue(sum-k, out count);
res+=count;
int val=0;
map.TryGetValue(sum, out val);
map[sum]=val+1;
}
return res;
}
}Time Complexity: O(n)
Space Complexity: O(n)
