Leetcode:523. Continuous Subarray Sum

c++code:

class Solution {  public:      bool checkSubarraySum(vector<int>& nums, int k) {          unordered_map<int, int> hash;          int sum = 0;          hash[0] = -1;          for(int i=0; i<nums.size(); ++i) {              sum += nums[i];              if(k) sum %= k;              if(hash.find(sum) != hash.end()) {                  if(i-hash[sum] > 1) return true;              }              else hash[sum] = i;          }          return false;      }  };