Merge pull request #101 from ritikpatel17/patch-5

 Trapping Rain Water

trap.java

@@ -0,0 +1,28 @@
+class Solution {
+    public int trap(int[] height) {
+        int []rightGtr = new int[height.length];
+        int []leftGtr = new int[height.length];
+        //left greater
+        for(int i=0; i<leftGtr.length; i++) {
+            if(i==0) leftGtr[i]=height[i];
+            else
+                leftGtr[i] = Math.max(leftGtr[i-1], height[i]);
+        }
+        //right greater
+        for(int i=rightGtr.length-1; i>=0; i--) {
+            if(i==rightGtr.length-1) rightGtr[i]=height[i];
+            else
+                rightGtr[i] = Math.max(rightGtr[i+1], height[i]);
+        }
+        // System.out.println(Arrays.toString(rightGtr));
+        int water =0;
+        for(int i=0; i<height.length; i++) {
+            int level = Math.min(rightGtr[i], leftGtr[i]);//waterlevel
+            if(level>=height[i])
+                water += level-height[i];
+
+        }
+
+        return water;
+    }
+}