#include<stdio.h>
#include<string.h>
int FindSubstr(char str[],char substr[])
{
    int i,j,n=0,count=0;
    int len1;
    int len2;
    len1=strlen(str);
    len2=strlen(substr);
    if(len1<len2)
    {
        return 0;
    }
    else
    {
        for(i=0;i<len1-len2;i++)
        {
            for(j=0;j<len2;j++)
            {
                if(substr[j]==str[i+j])
                {
                    n++;
                }
                else
                {
                    break;
                }
            }
                if(n==len2)
                {
                    count++;
                }
                n=0;
        }

    }
}
int main( )
{
    char str[100]={'\0'};
    char substr[100];
    int nsubstr=0;
    printf("please input str:\n");
    gets(str);
    printf("please input substr:\n");
    gets(substr);
    nsubstr=FindSubstr(str,substr);
    printf("%d\n",nsubstr);
    return 0;
}

子函数当中
else
要返回什么值？

跳出当前循环啊

子函数在else情况下也应该返回值要不你的函数在else情况下就没有返回值了，当然出错

我不明白你这个是做什么的，我当做是查找是否有字串来出来，输出0表示没找到 输出1表示找到了
#include<stdio.h>
#include<string.h>
int FindSubstr(char str[],char substr[])
{
    int i,j,n=0,count=0;
    int len1;
    int len2;
    len1=strlen(str);
    len2=strlen(substr);
    if(len1<len2)
    {
        return 0;
    }
    else
    {
        for(i=0;i<len1-len2;i++)/*这个改成i<=len1-len2*/
        {
            for(j=0;j<len2;j++)
            {
                if(substr[j]==str[i+j])
                {
                    n++;
                }
                else
                {
                    break;
                }
            }
                if(n==len2)
                {
                    count++;
                }
                n=0;
        }
       if(count>0)  /*加上这句*/
          return 1;
    }
}
int main( )
{
    char str[100]={'\0'};
    char substr[100];
    int nsubstr=0;
    printf("please input str:\n");
    gets(str);
    printf("please input substr:\n");
    gets(substr);
    nsubstr=FindSubstr(str,substr);
    printf("%d\n",nsubstr);
    return 0;
}