Problem: Trapping RainWater

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining.

Constraints: n == height.length 1 <= n <= 2 * 104 0 <= height[i] <= 105

class Solution {
    public int trap(int[] height) {
        int j = height.length-1;
        int[] left = new int[height.length];
        int[] right = new int[height.length];
        int leftMax = 0;
        int rightMax = 0;
        int i = 0;


        while(i<height.length){

            leftMax = Math.max(leftMax,height[i]);
            left[i] = leftMax;
            i++;
            rightMax = Math.max(rightMax,height[j]);
            right[j] = rightMax;
            j--;            
        }
        int sum = 0;
        for(i=0 ; i<height.length ; i++){
            sum += Math.min(left[i], right[i]) -height[i];
        }

        return sum;
    }
}