1092 : Absolute Difference Equation

时间限制Time Limit 5 秒Sec 内存限制Memory Limit 128 兆MB 提交次数Submitted 226 次Times 通过次数Solved 41 次Times

标准评测 Standard

从标准输入读入，结果写到标准输出。评测将输出拆成 token，与标准答案逐项比较，不按整段逐字节比对。 Read from standard input and write to standard output. The judge splits the output into tokens and compares them with the official answer; it does not compare raw bytes.

比对Compare	token 相同即通过。中间的空格、制表符、换行可多可少。Matching tokens pass. Extra spaces, tabs, or newlines between them are ignored.
不同则错Differs	token 个数或内容不同即错误。23 与 2 3、02 与 2、2.0 与 2 均视为不同。A different token count or value is wrong. 23 vs 2 3, 02 vs 2, and 2.0 vs 2 all differ.
输入Input	标准输入，格式见题面。Standard input; format as in the statement.
输出Output	标准输出。Standard output.

模板Template

C++ C Java Python

#include <iostream>
using namespace std;
int main() {
    int a, b;
    cin >> a >> b;
    cout << (a + b) << endl;
    return 0;
}

#include <stdio.h>
int main() {
    int a, b;
    scanf("%d%d", &a, &b);
    printf("%d\n", a + b);
    return 0;
}

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int a = in.nextInt();
        int b = in.nextInt();
        System.out.println(a + b);
    }
}

a, b = map(int, input().split())
print(a + b)

题目描述Description

For a sequence a₁, a₂, …, a_n, consider the following operation f: f(a) = {b₁, b₂, …, b_n − 1}, where b_i = |a_i − a_i + 1|.

After applying the operation f for n − 1 times, denoted by f^n − 1(a), the sequence will become a single element.

Bobo has a sequence a of length n filled with 0, 1 and ?. He would like to know the number of ways modulo (10⁹ + 7) to replace ? to 0 or 1 such that f^n − 1(a) = {1}.

输入格式Input

The input consists of several test cases terminated by end-of-file. For each test case:

The first line contains a nonempty string a consisting only of 0, 1 and ?, denoting the given sequence.

1 ≤ |a| ≤ 10⁶
The sum of |a| does not exceed 10⁷.

输出格式Output

For each test case, print an integer which denotes the result.

样例Sample

出题Author

ftiasch

来源Source

湖南省第十六届大学生计算机程序设计竞赛（HNCPC2020）