题解 | 连续子数组最大和

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        List<Integer>input = new ArrayList();
        int numLength = 0;
        boolean ifHavePos = false;
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            numLength = in.nextInt();
            break;
        }

        for (int i = 0; i < numLength; i++) {
            int num = in.nextInt();
            input.add(num);
            if (num >= 0 ) {
                ifHavePos = true;
            }
        }

        int sum = 0;

        int maxSum = ifHavePos? 0 : input.get(0);

        for (int i = 0; i < numLength; i++) {
            if (!ifHavePos) {
                maxSum = Math.max(maxSum, input.get(i));
            } else {
                if (input.get(i) < 0) {
                    sum += input.get(i);
                    if (sum < 0) {
                        sum -= input.get(i);
                        maxSum = Math.max(maxSum, sum);
                        sum = 0;
                    }
                } else {
                    sum += input.get(i);
                    maxSum = Math.max(maxSum, sum);
                }
            }

        }
        System.out.println(maxSum);
    }
}