[ACM] 常用程式片段

Debug用

#ifndef ONLINE_JUDGE
freopen("848_input.txt", "r",stdin);
freopen("848_output.txt","w",stdout);
#endif

進階版getch(), ungetch() (from K&R)

// ungetch(): push a char to stack
// getch(): if stack is not empty, pop a char
//          or get a char from stdin.

int buffer[1024];
int top = -1; //stack pointer

void ungetch(int c){
    buffer[++top] = c;
}

int getch(){
    if(top > -1)
        return buffer[top--];        
    else
        return getchar();
}