在 C++ 中输入一个矩阵？
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Input a matrix in c++?
提问by user2874452
I'm just a beginner of C++and I want to write a program which inputs and then displays a matrix of order i * j. I have written the following program but it did not work.
我只是一个初学者，C++我想编写一个程序，输入然后显示顺序矩阵i * j。我编写了以下程序，但它不起作用。
Kindly guide me .
请指导我。
I think may be the method of accessing is not right or something like that.
我想可能是访问方法不对或类似的东西。
Here is the program:
这是程序：
#include <iostream>
using namespace std;
int main() {
int i = 0,j = 0;
cout << "Enter no of rows of the matrix";
cin >> i;
cout << "Enter no of columns of the matrix";
cin >> j;
float l[i][j];
int p = 0, q = 0;
while (p < i) {
while (q < j) {
cout << "Enter the" << p + 1 << "*" << q + 1 << "entry";
cin >> l[p][q];
q = q + 1;
}
p = p + 1;
q = 0;
}
cout << l;
}
回答by Zac Wrangler
you cant define an array with variable length. You need to define a dynamic arrays or std::vector
你不能定义一个可变长度的数组。您需要定义一个动态数组或 std::vector
#include<vector>
std::vector<std::vector<int> > l(i, std::vector<int>(j, 0));
And cout << lwill only print out the value of a int**. To print out each individual integer, you need to loop against each of them.
并且cout << l只会打印出 a 的值int**。要打印出每个单独的整数，您需要对每个整数进行循环。
for(int x = 0; x < i; ++i){
for(int y = 0; y < j; ++y){
cout << l[x][y] << " "
}
cout << "\n";
}
回答by AndyBaba
I rewrote your code: (instead of alloc its better to use new in c++, and use delete to free the memory)
我重写了你的代码：（在c++中使用new而不是alloc更好，并使用delete来释放内存）
#include "stdafx.h"
#include<iostream>
#include <conio.h>
using namespace std;
int _tmain()
{
int row,col;
cout<<"Enter no of rows of the matrix";
cin>>row;
cout<<"Enter no of columns of the matrix";
cin>>col;
float** matrix = new float*[row];
for(int i = 0; i < row; ++i)
matrix[i] = new float[col];
int p=0,q=0;
for(unsigned i=0;i<row;i++) {
for(unsigned j=0;j<col;j++) {
cout<<"Enter the"<<i+1<<"*"<<j+1<<"entry";
cin>>matrix[i][j];
}
}
for(unsigned i=0;i<row;i++) {
for(unsigned j=0;j<col;j++) {
cout<<matrix[i][j]<<"\t";
}
cout<<endl;
}
getch();
return 0;
}
