[Error] 'a' was not declared in this scope如何解决

Question

#include<stdio.h>
#include<string.h>
#include<math.h>
int x,y,temp,a[n][n];
int n; 
int main()
{
    int transpose(int a[][]);    
    printf("input:\n");
    scanf("%d",&n);
    for(x=0;x<n;x++)
        {
        for(y=0;y<n;y++)
         {
            scanf("%d",&a[x][y]);
         }
        }
    transpose(a);
    for(x=0;x<n;x++)
        {
        for(y=0;y<n;y++)
        printf("%d ",a[x][y]);
        printf("\n");
         }
    
}
int transpose(int a[][])
{
    for(x=0;x<n;x++)
        for(y=x;y<n;y++)
            {
            temp=a[y][x];
            a[y][x]=a[x][y];
            a[x][y]=temp;
              }

}

出现了狠多错误 但是我不知道该怎么修改 是二维数组定义出错吗

Answer 1

数组的大小需要常数，修改如下，供参考：

#include<stdio.h>
#include<string.h>
#include<math.h>
#define N 20
int main()
{
    int x, y, temp, a[N][N];
    int n;
    int transpose(int a[][N], int n);
    printf("input:\n");
    scanf("%d", &n);
    for (x = 0; x < n; x++)
    {
        for (y = 0; y < n; y++)
        {
            scanf("%d", &a[x][y]);
        }
    }
    transpose(a, n);
    for (x = 0; x < n; x++)
    {
        for (y = 0; y < n; y++)
            printf("%d ", a[x][y]);
        printf("\n");
    }
}
int transpose(int a[][N],int n)
{
    int x, y, temp;
    for (x = 0; x < n; x++)
        for (y = x; y < n; y++)
        {
            temp = a[y][x];
            a[y][x] = a[x][y];
            a[x][y] = temp;
        }
    return 0;
}