Create 42. Trapping Rain Water (#455)

Author: Chayandas07

42. Trapping Rain Water

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+class Solution
+{
+public:
+    int trap(vector<int> &height)
+    {
+        int n = height.size(); // Number of elements in the input vector
+        int water = 0;     // Variable to store the total trapped water
+
+        // Arrays to store maximum height to the left and right of each index
+        vector<int> l_max(n), r_max(n);
+
+        // Calculate the maximum height to the left of each index
+        l_max[0] = height[0]; // First element's maximum height to the left is itself
+        for (int i = 1; i < n; i++)
+            l_max[i] = max(height[i], l_max[i - 1]);
+
+        // Calculate the maximum height to the right of each index
+        r_max[n - 1] = height[n - 1]; // Last element's maximum height to the right is itself
+        for (int i = n - 2; i >= 0; i--)
+            r_max[i] = max(height[i], r_max[i + 1]);
+
+        // Iterate through each index (excluding the first and last)
+        for (int i = 1; i < n - 1; i++)
+        {
+            // Calculate the maximum water current height can hold above itself
+            water += min(r_max[i], l_max[i]) - height[i];
+        }
+        return water; // Return the total trapped water
+    }
+};