向量分配崩溃 [英] Vector assignment crashing

问题描述

vector< vector<int> > resizeVector(vector< vector<int> > m)
{
    vector< vector<int> > newMatrix;
    int i,j;

    for (i = 0; i < m[i].size(); i++)
    {
        for(j = 0; j < m[j].size(); j++)
        {
            newMatrix[i][j] = m[i][j];
        }
    }
    return (newMatrix);
}

我正在编写一个程序，它将执行很多矩阵操作，而本节崩溃了，我不知道为什么.我将其范围缩小:

I am making a program that will do a whole lot of matrix manipulation, and this section is crashing and I don't exactly know why. I have narrowed it down to the line:

newMatrix[i][j] = m[i][j];

它在这里崩溃了，我不确定为什么.

It crashes right here, and I am not sure why.

推荐答案

除了@Saurav发布的内容外，newMatrix为空，因此您无法将值分配给newMatrix[i][j].您可以通过初始化给定大小的向量来解决此问题:

In addition to what @Saurav posted, newMatrix is empty so you cannot assign values to newMatrix[i][j]. You can fix this by initializing the vectors with a given size:

vector< vector<int> > resizeVector(vector< vector<int> > m)
{
    vector< vector<int> > newMatrix(m.size());
    int i,j;

    for (i = 0; i < m.size(); i++)
    {
        newMatrix[i].resize(m[i].size());
        for(j = 0; j < m[i].size(); j++)
        {
            newMatrix[i][j] = m[i][j];
        }
    }
    return (newMatrix);
}

在for循环之前，我们将newMatrix初始化为在其中包含m.size()许多空向量(由于其默认构造函数，这些向量为空).在外部for循环的每次迭代过程中，我们都使用resize成员函数确保newMatrix中的每个向量具有正确的大小.

Before the for-loops we initialize newMatrix to have m.size() many empty vectors inside of it (the vectors are empty due to their default constructor). During each iteration of the outer for-loop we ensure that each vector within newMatrix has the correct size using the resize member function.

请注意，如果您想要向量的副本，则只需编写以下内容即可:

Note that if you want a copy of a vector you can simply just write:

vector< vector<int> > newMatrix(m);

这篇关于向量分配崩溃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！