题解 | 喜欢切数组的红

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);
        int c =in.nextInt();
        int[] data = new int[c];
        for(int i=0;i<c;i++){
            data[i] = in.nextInt();
        }
        // 注意 hasNext 和 hasNextLine 的区别
        int[] qh = new int[data.length];
        //前缀和
        for (int i = 0; i < data.length; i++) {
            qh[i] = i > 0 ? qh[i - 1] + data[i] : data[i];
        }
        int sum = qh[data.length - 1];
        int z = sum / 3;
        if (z * 3 != sum){
            System.out.print(0);
            return;
        }
        int[] one = new int[data.length];
        int[] right = new int[data.length];
        int x = data.length;
        for (int i = data.length - 1; i >= 0; i--) {
            one[i] = x;
            if (data[i] > 0) x = i;
            if (i < data.length - 1) {
                right[i] = right[i + 1] + ((qh[i] == 2 * z) ? 1 : 0);
            }
        }

        int ans = 0;
        for (int i = 0; i < data.length; i++) {
            if (qh[i] == z && one[i] < data.length) ans += right[one[i]];
        }
        System.out.print(ans);
    }
}