萌新求问：自己编了strcpy，编译都出错，求问啊? 400 报错

萌新求问：自己编了strcpy，编译都出错，求问啊? 400 报错 void mystrcpy(char s1[], char s2[])
{
int len1 = 0;
while (s1[len1++]);
len1--;


int len2 = 0;
while (s2[len2++]);
len2--;


int i;
for (i = 0; i < len1; i++)
{
s1[i] = s2[i];
}
}


int main()
{
char sty1[100] = "hello ";
char sty2[100] = "world";
mystrcpy(sty1[100], sty2[100]);
printf("%s\n",sty1);


system("pause");
return 0;

}