编写一个函数，转换十进制数为字符串，需要处理负数，为什么会有错误呢

Question

/* 编写一个函数，转换字符串的逆序字符串，比如“ABC”转换为“CBA”。*/
void reverse(char r[],int n)
{
int i;
int temp;
for(i=0;i<n/2;i++)
{
temp=r[i];
r[i]=r[n-i-1];
r[n-i-1]=temp;

}
}
void chang1(int a)
{
int i = 0, j = 0, temp = 0;
char s[] = {NULL};

if ( a > 0)
{
    while ( a > 10)
    {
        temp = a%10;
        a = a/10;
        s[i] = temp + 48;
        i++;
        j++;
    }
    temp = a%10;
    a = a/10;
    s[i] = temp + 48;

    reverse(s,strlen(s));
    for ( i = 2; i <= j+2; i++ )
    {
        printf("%c",s[i]);
    }
}
else if ( a < 0)
{
    a = 0 - a;
    while ( a > 10)
    {
        temp = a%10;
        a = a/10;
        s[i] = temp + 48;
        i++;
        j++;
    }
    temp = a%10;
    a = a/10;
    s[i] = temp + 48;
    i++;
    s[i] = '-';
    reverse(s,strlen(s));
    for ( i = 1; i <= j+2; i++ )
    {
        printf("%c",s[i]);
    }
}
else if ( a == 0)
{
    printf("0");
}
else
{
    printf("输入有误\n");
}

}

Answer 1

char s[] = {NULL};没有分配足够空间，改为char s[100] = {0}