How can I make find_if function in this code?

Question

Edge {
    int source, dest, weight;
};

struct Node {
    int vertex, weight;
};

int main()
{
    vector<Edge> edges =
    {
    {0,1,2}, {0,2,3}, {1,3,-1}, {2,3,2}           // (edge1, edge2, weight)
    };

}

I want to create a function to see if the weight of the edge is negative or positive. How can I make the function?

Answer 1

我想创建一个函数，即使一个负权重为负，它也会输出 false。例如，如果第一个是 {0,1,-2} 而不是 {0,1,2} 它是假的

为什么要重新发明轮子？

如果我正确理解你想要什么，它是一个作品 std::all_of()

#include <vector>
#include <iostream>
#include <algorithm>

struct Edge
 { int source, dest, weight; };

int main ()
 {
   std::vector<Edge> edges1 { {0,1,2}, {0,2,3}, {1,3,-1}, {2,3,2} },
                     edges2 { {0,1,2}, {0,2,3}, {1,3,+1}, {2,3,2} };

   auto l = [](auto const & elem) { return elem.weight >= 0; };

   auto b1 { std::all_of(edges1.cbegin(), edges1.cend(), l) },
        b2 { std::all_of(edges2.cbegin(), edges2.cend(), l) };

   std::cout << b1 << std::endl; // prints 0
   std::cout << b2 << std::endl; // prints 1
 }

更一般地说，一个建议：尝试使用通过标准库可用的结构和算法。