C中动态分配的二维(双)数组 [英] Dynamically allocated two dimensional (double) array in C

问题描述

我正在尝试动态分配二维数组 N+1xN，所有元素都加倍.然后我想为数组的每个元素放置值 (1.6).最后一步是打印这个数组.我的功能

I'm trying to dynamically allocate two dimensional array N+1xN with all elements double. Then I want to put value (1.6) for each element of an array. The last step is to print this array. My function

void inic(double **t)
{
    for(int y=0;y<N;y++)
    {
        for(int x=0;x<N+1;x++)
        {
            t[x][y]=1.5;
        }
    }
}

无法正常工作，我不知道为什么.

isn't working as it should and I don't know why.

例如(对于 n=3)结果是:

For example the (for n=3) result is:

[0][0][0][0] 
[0][0][0][0] 
[0][0][0][0] 

我期望:

[1.6][1.6][1.6][1.6] 
[1.6][1.6][1.6][1.6] 
[1.6][1.6][1.6][1.6] 
[1.6][1.6][1.6][1.6] 

这是我的代码:

#include <stdio.h>
#include <stdlib.h>
int N;

void inic(double **t)
{
    for(int y=0;y<N;y++)
    {
        for(int x=0;x<N+1;x++)
        {

            t[x][y]=1.5;

        }
    }
}

void print(double **t)
{
    for(int y=0;y<N;y++)
    {
        for(int x=0;x<N+1;x++)
        {
            printf("%i ",t[x][y]);
        }
        printf("\n");
    }
}




int main()
{
    double **t;
    N=3;
    t=malloc((N+1)*sizeof(double*));
    for(int i=0;i<N+1;i++)
    {
        t[i]=malloc(N*sizeof(double));
    }

    inic(t);
    print(t);
    printf("\n");
}

推荐答案

您使用了不正确的转换说明符.试试下面的

You are using incorrect conversion specifier. Try the following

printf("%lf ",t[x][y]);

此外，使用另一个索引顺序会更自然，即本声明

Also it would be more natural to use another order of the indices that is when this statement

t=malloc((N)*sizeof(double*));

分配N行"，然后在循环中分配N+1列"

allocates N "rows" and then the N + 1 "columns" are allocated in the loop

for(int i=0;i<N;i++)
{
    t[i]=malloc( ( N + 1 )*sizeof(double));
}

在这种情况下，其他函数看起来像

In this case other functions will look like

void inic(double **t)
{
    for(int x = 0; x < N; x++)
    {
        for( int y = 0;  y < N + 1; y++ )
        {

            t[x][y]=1.5;

        }
    }
}

void print(double **t)
{
    for( int x = 0; x < N; x++ )
    {
        for( int y = 0; y < N + 1; y++)
        {
            printf("%lf ",t[x][y]);
        }
        printf("\n");
    }
}

此外，您应该在程序结束时释放所有分配的内存.

Also you should free all the allocated memory at the end of the program.

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