560. 和为 K 的子数组

test010.cpp

@@ -0,0 +1,20 @@
+class Solution {
+public:
+    int subarraySum(vector<int>& nums, int k) {
+        int n = nums.size();
+        vector<int> p(n+1, 0);
+        for(int i = 1; i <= n; i++){
+            p[i] = p[i - 1] + nums[i - 1];
+        }
+        int ret = 0;
+        unordered_map<int, int> data;
+        for(int l = n; l; l--){
+            data[p[l]]++;
+            int target = k + p[l-1];
+            if(data.count(target)){
+                ret += data[target];
+            }
+        }
+        return ret;
+    }
+};