在C ++中解析格式化的用户输入 [英] Parsing formatted user input in C++

问题描述

对于一个项目，我需要实现图形着色问题的解决方案。但是，输入需要具有特定的语法，我不知道如何解析通过，以访问存储在变量中需要的数据。

For a project I need to implement a solution to the graph coloring problem. However, the input is required to have specific syntax with which I have no idea on how to parse through in order to access the data needed to store in variables.

输入约束是先输入颜色数，然后是顶点数，后跟一系列边。边应以（v1 v2）的格式输入。序列以v1 = -1结束。因此，（ - 1 0），（ - 1 -1）等。

The input constraints are to first enter the number of colors, then the number of vertices, followed by a sequence of edges. The edges should be entered in the format (v1 v2). The sequence is terminated with v1 = -1. So, (-1 0), (-1 -1), etc.

所以输入的结果是：

2 4 (0 1)(1 2)(2 3)(3 0)(-1 -1)

将非常感谢，因为我不知道哪里甚至开始！我知道这里有类似的问题，但我不知道如何应用他们的解决方案为这个具体的实现。

Any help would be greatly appreciated, as I have no idea where to even begin! I know there are similar questions here, however I can't figure out how to apply their solutions for this specific implementation.

推荐答案

尝试这样：

#include <iostream>

static inline int error(int n) { std::cerr << "Input error!\n"; return n; }

int main()
{
    int nc, nv;  // number of colours and vertices

    if (!(std::cin >> nc >> nv)) { return error(1); }

    for (int i = 0; i != nv; ++i)
    {
        char lb, rb;
        int v1, v2;
        if (!(std::cin >> lb >> v1 >> v2 >> rb) || lb != '(' || rb != ')') { return error(1); }

        std::cout << "We have a pair [" << v1 << ", " << v2 << "]\n";
    }
}

注意输入处理的关键原理：出现在条件上下文中。因为@jedwards说，输入可以是任何 std :: istream ，如字符串流或文件流，或在我的例子 std :: cin 。

Note the key principle of input processing: All input operations appear inside a conditional context. As @jedwards says, the input can be any std::istream, such as a string stream or a file stream, or as in my example std::cin.

这篇关于在C ++中解析格式化的用户输入的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！