Trapping Rain Water (in C++)

Please add this new file for the issue that I have raised for issue #1055

Trapping Rain Water

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+#include<iostream>
+#include<vector>
+#include<algorithm>
+#include<cmath>
+using namespace std;
+
+int trap(vector<int>& heights) {
+    if(heights.size()<=2){
+        return 0;
+    }
+    vector<int> leftToRight;
+    int maxHeight = heights[0]; 
+    for(int i = 0; i < heights.size(); i++){
+        maxHeight = max(maxHeight , heights[i]);
+        leftToRight.push_back(maxHeight - heights[i]);
+    }
+    vector<int> rightToLeft;
+    maxHeight = heights[heights.size() - 1];
+    for(int i = heights.size() - 1; i >= 0; i--){
+        maxHeight = max(maxHeight , heights[i]);
+        rightToLeft.push_back(maxHeight - heights[i]);
+    }
+    reverse(rightToLeft.begin() , rightToLeft.end());
+    int ans = 0;
+    for(int i = 0; i < heights.size(); i++){
+        ans += min(leftToRight[i] , rightToLeft[i]);
+    }
+    return ans;
+}
+int main(){
+    int n;
+    cin>>n;
+    vector<int> heights(n,0);
+    for(int i=0;i<n;i++){
+        cin>>heights[i];
+    }
+    int waterTrapped=trap(heights);
+    cout<<waterTrapped;
+    return 0;
+}