title
Given an array of integers and an integer k, you need to find the total number of continuous subarrays whose sum equals to k.
Example 1:
Input:nums = [1,1,1], k = 2
Output: 2
Note:
The length of the array is in range [1, 20,000].
The range of numbers in the array is [-1000, 1000] and the range of the integer k is [-1e7, 1e7].
solution
记录sum即可
class Solution {
public:
int subarraySum(vector<int>& nums, int k) {
int sum = 0, res = 0;
unordered_map<int, int> map1;
map1[0] = 1;
for (int i = 0; i < nums.size(); i++) {
sum += nums[i];
if (map1.count(sum - k)) {
res += map1.at(sum - k);
}
map1[sum]++;
}
return res;
}
};