[leetcode]560. Subarray Sum Equals K
Analysis
ummm 心情复杂—— [每天刷题并不难0.0]
Given an array of integers and an integer k, you need to find the total number of continuous subarrays whose sum equals to k.
Explanation:
计算pre sum,再结合hashmap就可以了
Implement
class Solution {
public:
int subarraySum(vector<int>& nums, int k) {
int len = nums.size();
unordered_map<int, int> cnt_sum;
cnt_sum[0]++;
int sum = 0;
int res = 0;
for(int i=0; i<len; i++){
sum += nums[i];
if(cnt_sum.count(sum-k))
res += cnt_sum[sum-k];
cnt_sum[sum]++;
}
return res;
}
};