Create TrappingRainWater.java

This Is An Easy Solution To The Hard Problem Of LeetCode 'Trapping RainWater'
People Usually Get Scared To This Problem Because Of The Dynamic Programming Tag
But I Have Solved This Using Two Arrays
We Can Use Stack For Better Solution

Author: akashSky369

TrappingRainWater.java

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+  public int trap(int[] height) {
+        int[] left = new int[height.length]; //for left most height for every tower
+        int[] right = new int[height.length]; //for right most height for every tower
+        int n = height.length;
+        
+        int ctr = height[0];
+        for(int i =0; i<n; i++){
+            ctr = Math.max(ctr,height[i]);
+            
+            left[i] = ctr;
+        }
+        
+        ctr = height[n-1];
+        for(int i =n-1; i>=0; i--){
+            ctr = Math.max(ctr,height[i]);
+            right[i] = ctr;
+        }
+        int res = 0;
+        
+        for(int i =0; i<n; i++){
+            res += Math.min(left[i], right[i])-height[i];//water for every tower
+        }
+        
+        return res;
+    }