牛客网：获得最多的奖金（双指针）

牛客网：获得最多的奖金（双指针）

1.题目链接

https://www.nowcoder.com/practice/247f7bd088764aefa7474cff27489095?tpId=98&tqId=32839&tPage=1&rp=1&ru=/ta/2019test&qru=/ta/2019test/question-ranking

2.分析

用头指针begin和尾指针end，两边向中间靠拢

左边部分的总和为leftValue（0 ~ begin），右边部分的总和为rightValue(end ~ lengh - 1)

有三种情况：

1. leftValue == rightValue

   记录此时两者的值为max

2. leftValue > rightValue

   end指针减1，rightValue = rightValue + arr[end]

3. leftValue < rightValue

   begin指针加1，leftValue = leftValue + arr[begin]

3.代码

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        int[] arr = new int[num];
        for(int i = 0; i < num; i++){
            arr[i] = sc.nextInt();
        }
        int begin = -1;
        int end = arr.length;
        long leftValue = 0;
        long rightValue = 0;
        long max = 0;
        while(begin != end){
            if(leftValue == rightValue){
                max = leftValue;
                leftValue += arr[++begin];
            }else if(leftValue > rightValue){
                end--;
                rightValue += arr[end];
            }else if(leftValue < rightValue){
                begin++;
                leftValue += arr[begin];
            }
        }
        System.out.println(max);
    }
}