算法实现柱形集合积水面积

用一个数组代表柱形墙的的高度。当下雨的时候柱形墙能积水的体积是多少

下面是python的实现算法：

# -*- coding: utf-8 -*-
def savewater(arr):
    point_l=0
    max_l=arr[0]
    point_r=len(arr)-1
    max_r=arr[len(arr)-1]
    volume=0
    #point_l从左向右遍历,point_r从右向左遍历
    while point_l<point_r:
        #能积水的标准时两边的高度大于中间的
        if max_l<max_r:
            point_l=point_l+1
            if max_l<=arr[point_l]:
                max_l=arr[point_l]
            else:
                volume=volume+max_l-arr[point_l]
        else:
            point_r=point_r-1
            if max_r<=arr[point_r]:
                max_r=arr[point_r]
            else:
                volume=volume+max_r-arr[point_r]
    return volume
    
    
if __name__=='__main__':
    arr=[1,2,3,4,2,1,1,5,3,2]
    volume=savewater(arr)
    print volume

java实现算法：

package com.gh.d1;

/**
 * Created by Lenovo on 2014/12/29.
 */
public class D1_1 {
    public static void main(String[] args){
        int[] array=new int[]{1,2,3,4,2,1,1,5,3,2};
        int volume=savewater(array);
        System.out.println(volume);
    }
    public static int savewater(int[] array) {
        int point_l = 0;
        int max_l = 0;
        int point_r = array.length;
        int max_r = array[array.length - 1];
        int volume = 0;
        while (point_l < point_r) {
            if (max_l < max_r) {
                point_l++;
                if (max_l <= array[point_l]) {
                    max_l = array[point_l];
                } else {
                    volume = volume + max_l - array[point_l];
                }
            } else {
                point_r--;
                if (max_r <= array[point_r]) {
                    max_r = array[point_r];
                } else {
                    volume = volume + max_r - array[point_r];
                }
            }
        }
        return volume;
    }
}

golang实现：

package main

import (
    "fmt"
)

func main() {
    arr := []int{1, 2, 3, 4, 2, 1, 1, 5, 3, 2}
    volume := savewater(arr)
    fmt.Println(volume)
}
func savewater(arr []int) int {
    point_l := 0
    max_l := 0
    point_r := len(arr) - 1
    max_r := arr[len(arr)-1]
    volume := 0
    for point_l < point_r {
        if max_l < max_r {
            point_l++
            if max_l < arr[point_l] {
                max_l = arr[point_l]
            } else {
                volume = volume + max_l - arr[point_l]
            }
        } else {
            point_r--
            if max_r < arr[point_r] {
                max_r = arr[point_r]
            } else {
                volume = volume + max_r - arr[point_r]
            }
        }
    }
    return volume
}