Adding TrappingRainWater solution

java-program/TrappingRainWater.java

@@ -0,0 +1,55 @@
+import java.io.*;
+import java.util.*;
+import java.lang.*;
+
+class TrappingRainWater{
+  public static void main(String[] args) throws IOException{
+    BufferReader br = new BufferedReader(new InputStreamReader(System.in));
+    int t = Integer.parseInt(br.readLine().trim());
+    int arr[] = new int[n];
+    while(t --> 0){
+      int n = Integer.parseInt(br.readLine().trim());
+      int arr[] = new int[n];
+      String inputLine[] = br.readLine().trim().split(" ");
+
+      for(int i=0;i<n;i++){
+        arr[i] = Integer.parseInt(inputLine[i]);
+      }
+      Solution obj = new Solution();
+      System.out.println(obj.trappingWater(arr,n));
+    }
+  }
+}
+
+
+class Solution{
+
+    static long trappingWater(int arr[], int n) { 
+        int len = arr.length;
+        int[] leftArr = new int[len];
+        int[] rightArr = new int[len];
+        int max = Integer.MIN_VALUE;
+        for(int i=0; i<len; i++){
+            if(max < arr[i]){
+                max = arr[i];
+            }
+            leftArr[i] = max;
+        }
+
+        max = Integer.MIN_VALUE;
+        for(int i=len-1; i>=0; i--){
+            if(max < arr[i]){
+                max = arr[i];
+            }
+            rightArr[i] = max;
+        }
+
+        long totalWater = 0;
+
+        for(int i=0; i<len; i++){
+            totalWater += Math.min(leftArr[i],rightArr[i]) - arr[i];
+        }
+
+        return totalWater;
+    } 
+}