Create continuous-subarray-sum.cpp

Author: kamyu104

C++/continuous-subarray-sum.cpp

@@ -0,0 +1,25 @@
+// Time:  O(n)
+// Space: O(k)
+
+class Solution {
+public:
+    bool checkSubarraySum(vector<int>& nums, int k) {
+        int count = 0;
+        unordered_map<int, int> lookup;
+        lookup[0] = -1;
+        for (int i = 0; i < nums.size(); ++i) {
+            count += nums[i];
+            if (k != 0) {
+                count %= k; 
+            }
+            if (lookup.count(count)) {
+                if (i - lookup[count] > 1) {
+                    return true;
+                }
+            } else {
+                lookup[count] = i;
+            }
+        }
+        return false;
+    }
+};