2-4 does not terminate

[swy20190]

I find the program does not terminate on Windows.
But the following code works:

void squeeze(char s1[], char s2[])
{
    int i=0;//s1 ptr
    char tmp[MAXLINE];
    int k=0;//tmp ptr
    while(s1[i]!='\0'){
        int find_flag = 0;
        int j=0;//s2 ptr
        while(s2[j]!='\0'){
            if(s1[i]==s2[j]){//match!
                find_flag=1;
                break;
            }
            j++;
        }
        if(find_flag==0){
            tmp[k]=s1[i];
            k++;
        }
        i++;
    }
    tmp[k]='\0';
    for(int ii=0;ii<k+1;ii++)
        s1[ii]=tmp[ii];
}