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  • 杭电 oj 3350 #define is unsafe

    #define is unsafe

    Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
    Total Submission(s): 568 Accepted Submission(s): 359

    Problem Description
    Have you used #define in C/C++ code like the code below?

    #include <stdio.h>
    #define MAX(a , b) ((a) > (b) ? (a) : (b))
    int main()
    {
    printf(“%d ” , MAX(2 + 3 , 4));
    return 0;
    }

    Run the code and get an output: 5, right?
    You may think it is equal to this code:

    #include <stdio.h>
    int max(a , b) { return ((a) > (b) ? (a) : (b)); }
    int main()
    {
    printf(“%d ” , max(2 + 3 , 4));
    return 0;
    }

    But they aren’t.Though they do produce the same anwser , they work in two different ways.
    The first code, just replace the MAX(2 + 3 , 4) with ((2 + 3) > (4) ? (2 + 3) : 4), which calculates (2 + 3) twice.
    While the second calculates (2 + 3) first, and send the value (5 , 4) to function max(a , b) , which calculates (2 + 3) only once.

    What about MAX( MAX(1+2,2) , 3 ) ?
    Remember “replace”.
    First replace: MAX( (1 + 2) > 2 ? (1 + 2) : 2 , 3)
    Second replace: ( ( ( 1 + 2 ) > 2 ? ( 1 + 2 ) : 2 ) > 3 ? ( ( 1 + 2 ) > 2 ? ( 1 + 2 ) : 2 ) : 3).
    The code may calculate the same expression many times like ( 1 + 2 ) above.
    So #define isn’t good.In this problem,I’ll give you some strings, tell me the result and how many additions(加法) are computed.

    Input
    The first line is an integer T(T<=40) indicating case number.
    The next T lines each has a string(no longer than 1000), with MAX(a,b), digits, ‘+’ only(Yes, there’re no other characters).
    In MAX(a,b), a and b may be a string with MAX(c,d), digits, ‘+’.See the sample and things will be clearer.

    Output
    For each case, output two integers in a line separated by a single space.Integers in output won’t exceed 1000000.

    Sample Input
    6
    MAX(1,0)
    1+MAX(1,0)
    MAX(2+1,3)
    MAX(4,2+2)
    MAX(1+1,2)+MAX(2,3)
    MAX(MAX(1+2,3),MAX(4+5+6,MAX(7+8,9)))+MAX(10,MAX(MAX(11,12),13))

    Sample Output
    1 0
    2 1
    3 1
    4 2
    5 2
    28 14

    #include<iostream>
    #include<algorithm>
    #include<cstring>
    #include<cstdio>
    #include<stack>
    using namespace std;
    struct asdf
    {
        int tot,num;
    }tem,in,out;
    stack<asdf>st;//保存数据的 信息
    stack<char>cs;//保存 运算符
    int n,m;
    char s[10005];
    int main()
    {
        int t;
        cin>>t;
        getchar();
        while(t--)
        {
            gets(s);
            int len=strlen(s);
            for(int i=0;i<len;i++)
            {
                if(s[i]>='0'&&s[i]<='9')
                {
                    int te=0;
                    while(s[i]<='9'&&s[i]>='0')//计算数字  值
                    {
                        te=te*10+s[i]-'0';
                        i++;
                    }
                    if(!cs.empty()&&cs.top()=='+')
                    {
                        tem=st.top();
                        st.pop();
                        tem.num+=te;//计算和
                        tem.tot++;//加法 加一
                        st.push(tem);
                        cs.pop();
                    }
                    else
                    {
                        tem.num=te;//第一个直接入栈
                        tem.tot=0;//加法个数
                        st.push(tem);
                    }
                    i--;
                }
                else if(s[i]=='+'||s[i]=='(')
                {
                    cs.push(s[i]);//直接入栈  方便计算加法个数   和和
                }
                else if(s[i]==')'||s[i]==',')//
                {//满足条件时候 向前运算 
                    while(!cs.empty()&&cs.top()=='+')
                    {
                        in=st.top();
                        st.pop();
                        out=st.top();
                        st.pop();
                        tem.tot=in.tot+out.tot+1;//多次加法 (⊙o⊙)
                        tem.num=in.num+out.num;//求和
                        st.push(tem);
                        cs.pop();//入栈
                    }
                    if(s[i]==')'&&st.size()>=2)
                    {
                        in=st.top();
                        st.pop();
                        out=st.top();
                        st.pop();
                        tem.num=in.num+out.num;//求和
                        if(out.num>in.num)
                        {
                            out.tot=out.tot*2+in.tot;//根据题目要求统计和大的那个数的加法个数
                            st.push(out);//加法的个数*2  因为它MAX(MAX()) 等情况时间 MAX中的加法 是成倍增加的 
                        }
                        else
                        {
                            in.tot=in.tot*2+out.tot;
                            st.push(in);
                        }
                        cs.pop();
                    }
                }
            }
            while(!cs.empty())//不为空 且没有MAX时间
            {
                while(!cs.empty()&&cs.top()=='+')//同上
                {
                    in=st.top();
                    st.pop();
                    out=st.top();
                    st.pop();
                    tem.tot=in.tot+out.tot+1;//累加 加法个数
                    tem.num=in.num+out.num;
                    st.push(tem);
                    cs.pop();
                }
            }
            cout<<st.top().num<<" "<<st.top().tot<<endl;
            st.pop();//清空栈   
        }
        return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/nanfenggu/p/7900175.html
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