打印矢量 [英] Print a vector of vectors

问题描述

我正在尝试在c ++中打印一个二维数组，但是我遇到了问题.我遵循传统的方法在for循环中打印矢量vectorName.size().所以我遵循的方式是这样.

I'm trying to print a bidimensional array in c++ but I have a problem. I followed the traditional way to print a vector vectorName.size() inside a for loop. So the way that I follow was this.

#include <stdio.h>
#include <iostream>
#include <vector>
#include <math.h>
#include <time.h>


using namespace std;

void impMat(vector < vector <int> >, vector < vector <int> >);

int main () {
    vector < vector <int> > A;
    vector < vector <int> > B;
    vector <int> temp;

    for(int j = 0; j < 4; j++){
       for(int i = 0; i < 5; i++){
          temp.push_back(i);
       }
       A.push_back(temp);
       B.push_back(temp);
    }

    impMat(A,B);
    cout << endl;
    return 0;
}

void impMat(vector < vector <int> > A,vector < vector <int> > B) 
{
    for(int i = 0; i < A.size(); i++){
       for(int j = 0; j < A[i].size(); j++){
          cout << A[i][j] << " ";
       }
       cout << endl;
    }
    cout << endl;
    for(int i = 0; i < B.size(); i++){
       for(int j = 0; j < B[i].size(); j++){
          cout << B[i][j] << " ";
       }
       cout << endl;
    }
}

但这就是这样打印

0 1 2 3 4
0 1 2 3 4 0 1 2 3 4
0 1 2 3 4 0 1 2 3 4 0 1 2 3 4
0 1 2 3 4 0 1 2 3 4 0 1 2 3 4 0 1 2 3 4

预期输出

0 1 2 3 4 
0 1 2 3 4
0 1 2 3 4
0 1 2 3 4

如何正确打印矢量?

推荐答案

问题基本上是如何填充向量:

The problem basically is how you fill your vectors:

for(int j = 0; j < 4; j++)
{
     for(int i = 0; i < 5; i++)
     {
          temp.push_back(i);
     }
     A.push_back(temp);
     B.push_back(temp);
     // now temp yet contains all the values entered, so you produce:
     // 0, 1, 2, 3, 4 in first loop run,
     // 0, 1, 2, 3, 4 0, 1, 2, 3, 4 in second,
     // ...
     // most simple fix:
     temp.clear();
}

不过，由于您仍然希望拥有相同的数据，因此效率更高:

More efficient, though, as you want to have the same data anyway:

for(int i = 0; i < 5; i++)
{
     temp.push_back(i);
}

for(int i = 0; i < 4; i++)
{
     A.push_back(temp);
     B.push_back(temp);
}

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