leetcode 和为 k 的子数组

Posted 2021-08-25 Wh1t3zZ

 

 

两题如出一辙：https://www.cnblogs.com/rookie-acmer/p/15164840.html

class Solution {
public:
    int subarraySum(const vector<int>& nums, const int &k) {
        unordered_map<int, int> cnt;
        int ret = 0, preSum = 0;
        cnt[0] = 1;     // 初始状态
        for(int i = 0; i < nums.size(); ++ i) {
            preSum += nums[i];
            ret += cnt[preSum - k];
            ++ cnt[preSum];
        }
        return ret;
    }
};