1105 : Directed Chain Decomposition

时间限制Time Limit 2 秒Sec 内存限制Memory Limit 128 兆MB 提交次数Submitted 3 次Times 通过次数Solved 1 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.
时间与内存Time and memory	记这一份程序的 CPU 时间和内存峰值。题目上的时间限制、内存限制就是这一份的上限。The record is this program’s CPU time and peak memory. The limits on the problem apply to this one run.

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

There is a tree with n nodes (labeled 1, 2, …, n) and n − 1 directed edges. We can decompose the tree into several directed chains, and each edge appears in exactly one chain. Now you need to figure out the minimum number of edges that we need to reverse in order to minimize the minimum possible number of directed chains in the decomposition result.

For example, if we have a tree 1 → 2 → 3 ← 4, we can reverse the edge from node 4 to node 3, then the tree can be decomposed into only one directed chain.

输入格式Input

There will be at most 200 test cases. Each case begins with one integer n(3 ≤ n ≤ 10⁵), the number of nodes. Each of the following n − 1 lines contains two integers u_i, v_i(1 ≤ u_i, v_i ≤ n, u_i ≠ v_i), denoting a directed edge from node u_i to node v_i. The size of the whole input file does not exceed 8MB.

输出格式Output

For each test case, print the minimum possible number of directed chains in the decomposition result, and the minimum number of edges that we need to reverse.

CSGCPC

1105 : Directed Chain Decomposition

题目描述Description

输入格式Input

输出格式Output

样例Sample

出题Author

来源Source