题解 | #没有重复项数字的所有排列#

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
        if (arr == null || arr.length < 3) {
            return 0;
        }
        int left = 0, right = arr.length - 1;
        long maxLeft = 0, maxRight = 0, ans = 0;
        /*
        3,1,2,5,2,4
        */
        while (left <= right) {
            if (maxLeft < maxRight) {
                ans += Math.max(0, maxLeft - arr[left]);
                maxLeft = Math.max(maxLeft,arr[left]);
                left++;
            } else {
                ans += Math.max(0, maxRight - arr[right]);
                maxRight = Math.max(maxRight,arr[right]);
                right--;
            }
        }
        return ans;
    }
}