练习3.19 计算后缀表达式的值

int main()
{
    int MaxSize = 100,i,j;
    char tmp[10];
    PtrToStack s;
    s = CreateStack(MaxSize);
    while( scanf("%s",tmp) != EOF )
    {
        int len,num=0,val1,val2;
        len = strlen(tmp);
        if( tmp[0] == ‘\n‘)
            break;
        if( len == 1 && tmp[0] >=48 && tmp[0] <= 57 )
            Push( tmp[0] - ‘0‘, s );
        else if( len > 1 )
        {
            for( i = 0,j = len - 1; i < len; i++,j--)
            {
                num += tmp[i] * pow(10,j);
            }
            Push( num, s);
        }
        else
        {
            val1 = Top(s);
            Pop(s);
            val2 = Top(s);
            Pop(s);
            switch ( tmp[0] )
            {
            case ‘+‘:
                Push( val1 + val2, s );
                break;
            case ‘-‘:
                Push( val1 - val2, s );
                break;
            case ‘*‘:
                Push( val1 * val2, s );
                break;
            case ‘/‘:
                Push( val1 / val2, s );
                break;
            }
        }//else
    }//while
    printf("%d", Top(s) );
}