The input is two strings(A and B) and a integer(k).
You should write a function to accomplish the following functions.
1、Insert B into A, the integer k is the position of the B.
    Example: A is "World", B is "Hello", k=0, the result is "HelloWorld"
2、if k < 0 or k > strlen(A), print "illegal index"
3、The length of A is less then 2000, the length of B is less than 1000.
Sample Input:
world hello 0
Sample Output:
helloworld

Sample Input:
world hello 10
Sample Output:
illegal index

Sample Input:
helld oworl 4
Sample Output:
helloworld

可以看看这个,输入字符串去掉空格等无效字符可以这样简单处理(不过要注意缓冲区溢出问题,其实正常来说应该是用fgets从缓冲区里面来读取字符的)~

#include<stdio.h>

void fun( char*,const char*,size_t );

int main( void )
{
    char A[2000];
    char B[1000];
    
    int index;
    
    scanf("%s%s%d",A,B,&index);
    
    fun(A,B,index);
    
    return 0;
}

#include<stdlib.h>
#include<string.h>
#include<assert.h>

void fun( char* A,const char* B,int len )
{
    assert(A);
    assert(B);
    
    {
        const unsigned a_len=strlen(A);
        const unsigned b_len=strlen(B);
    
        if (len<0||len>a_len)
        {
            puts("illegal index");
            
            return ;
        }
        
        memmove(A+len+b_len,A+len,a_len-len+1);
        memmove(A+len,B,b_len);
    }
   
   puts(A);
}

[此贴子已经被作者于2018-4-23 23:37编辑过]

其余同学请绕行，谢谢