NC128 接雨水问题

import java.util.*;
public class Solution {
    /**
     * max water
     * @param arr int整型一维数组 the array
     * @return long长整型
     */
    public long maxWater (int[] arr) {
        // write code here
        int l = 0, r = arr.length - 1, i = l, j = r;
        long v = 0;
        while (i < j) {
            if (arr[l] < arr[r]) {
                if (arr[++i] < arr[l]) {
                    v += arr[l] - arr[i];
                } else {
                    l = i;
                }
            } else {
                if (arr[--j] < arr[r]) {
                    v += arr[r] - arr[j];
                } else {
                    r = j;
                }
            }
        }
        return v;
    }
}