Created Trapping_Rain_Water.cpp using c++

C++ program to find maximum amount of water that can be trapped within given set of bars.

Author: avinitd

Trapping_rain_Water.cpp

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+// This code is contributed by Avinash Prasad (GitHub : avinash11a)
+// C++ program to find maximum amount of water that can 
+// be trapped within given set of bars. 
+// Space Complexity : O(1) 
+
+#include<iostream> 
+using namespace std; 
+
+int findWater(int arr[], int n) 
+{ 
+	// initialize output 
+	int result = 0; 
+	
+	// maximum element on left and right 
+	int left_max = 0, right_max = 0; 
+	
+	// indices to traverse the array 
+	int lo = 0, hi = n-1; 
+	
+	while(lo <= hi) 
+	{ 
+		if(arr[lo] < arr[hi]) 
+		{ 
+			if(arr[lo] > left_max) 
+			// update max in left 
+			left_max = arr[lo]; 
+			else
+			// water on curr element = max - curr 
+			result += left_max - arr[lo]; 
+			lo++; 
+		} 
+		else
+		{ 
+			if(arr[hi] > right_max) 
+			// update right maximum 
+			right_max = arr[hi]; 
+			else
+			result += right_max - arr[hi]; 
+			hi--; 
+		} 
+	} 
+	
+	return result; 
+} 
+
+int main() 
+{ 
+	int arr[] = {0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1}; 
+	int n = sizeof(arr)/sizeof(arr[0]); 
+	cout << "Maximum water that can be accumulated is "
+		<< findWater(arr, n); 
+} 
+
+// This code is contributed by Avinash Prasad