如何从数组传递到向量-C ++

Question

I'm new in c++ programming and I'm trying to understand better the differences between array and vector. In my program I've got a class Graph with some arrays as private members. The class has a method that use these arrays to implement the Prim's algorithm for minimum spanning tree. I took the algorithm from this page and changed it for my program.

I am now asked to use vectors instead of arrays so I would like to know:

How many things do I really have to change? The declaration and the constructors, ok. But the cycles, the initializations. Do I have to change everything? The program works anyway. Is it so important to use vector's function?

Answer 1

It should be very simple to switch from arrays to a vector . You could initialise the vector with the size of your array and fill it with 0 elements:

vector<YourType> v(size_of_array, YourType(0));

and then use v more or less as you used your array, ie:

v[x] = YourType(y);
// ....
f(v[z]);

etc

Answer 2

I took a look at the code at your link above and spotted quite a few places where STL vectors can be used rather than the arrays that are defined.

For example, below is an example of how to replace a couple of the arrays with vectors, and then initialize their values:

#include <iostream>
#include <limits>
#include <vector>

// Number of vertices in the graph
static const int V = 5;

int main()
{
    // Rather than use:
    // int key[V];
    // bool mstSet[V];

    // You could setup STL vector containers:
    std::vector<int> key;
    std::vector<bool> mstSet;

    // Next, initialize:
    for (size_t i = 0; i < V; i++) {
        key.push_back(INT_MAX);
        mstSet.push_back(false);
        std::cout << key[i] << "; " << mstSet[i] << std::endl;
    }

    return 0;
}

Answer 3

如果要坚持使用当前的实现，但想尝试使用向量，则可以通过以下方式用数组数据填充向量：

vec.assign(arr, arr + arr_size);