RainTrapped.java

public class RainTrapped {
    public static int Trappedrainwater(int height[]){
      int n=height.length;

       
      //calculate left max boundary-array
      int leftMax[]=new int [n];
      leftMax[0]=height[0];
      for(int i=1;i<n;i++){
      leftMax[i]=Math.max(height[i],leftMax[i-1]);
      }



      //calculate right max boundary-array
      int rightMax[]=new int [n];
      rightMax[n-1]=height[n-1];
      for(int i=n-2;i>=0;i--){
        rightMax[i]=Math.max(height[i],rightMax[i+1]);
        
      }
      

      //to trappedwater
      int trappedwater=0;
      for(int i=0;i<n;i++){
        int waterlevel=Math.min(leftMax[i],rightMax[i]);
        trappedwater+=waterlevel-height[i];
      }
      
      return trappedwater;
      
      
    }

    public static void main(String args[]){
        int height[]={4,2,0,6,3,2,5};
        System.out.println("rainwater ratio is :"+Trappedrainwater(height));
    }

}