rainwater.java

public class rainwater
{
      public int trap(int[] height) {
            int left = 0;
            int right = height.length - 1;
            int leftMax = height[left];
            int rightMax = height[right];
            int res = 0;
            while(left < right){
                  if(leftMax< rightMax){
                        left++;
                        leftMax = Math.max(height[left], leftMax);
                        res += leftMax - height[left];
                  }
                  else
                  {
                        right--;
                        rightMax = Math.max(height[right], rightMax);
                        res += rightMax - height[right];
                  }
            }
            return res;
      }

	public static void main(String[] args) {
		int arr[]={4,2,0,6,3,2,5};
		TrappingRainwater(arr);
	}
}