Create 930.Binary-Subarrays-With-Sum_v2.cpp

CharlesChou03 · May 21, 2022 · 3a30051 · 3a30051
1 parent 7545bae
commit 3a30051
Showing 1 changed file with 34 additions and 0 deletions.
diff --git a/Hash/930.Binary-Subarrays-With-Sum/930.Binary-Subarrays-With-Sum_v2.cpp b/Hash/930.Binary-Subarrays-With-Sum/930.Binary-Subarrays-With-Sum_v2.cpp
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+class Solution {
+public:
+    int numSubarraysWithSum(vector<int>& A, int S) 
+    {       
+        int n = A.size();
+        vector<int>postZeros(n);
+        int count = 0;
+        for (int i=n-1; i>=0; i--)
+        {
+            postZeros[i] = count;
+            if (A[i]==0)            
+                count++;            
+            else
+                count = 0;
+        }
+
+        int j = 0, sum = 0;
+        int ret = 0;
+        for (int i=0; i<n; i++)
+        {
+            while (j<=i || (j<n && sum < S))
+            {
+                sum += A[j];
+                j++;
+            }
+
+            if (sum==S)
+                ret += postZeros[j-1]+1;
+            sum -= A[i]; 
+        }
+
+        return ret;        
+    }
+};