枚举+计算器模拟——hdu 4192

http://acm.hdu.edu.cn/showproblem.php?pid=4192

这道题A的好辛苦啊！！！

易错点：开始时 a,b当做个位数在考虑

2 42 93 11
(a-b)

就会错，哎思维不严密啊！！！

#include<iostream>
#include<algorithm>
#include<cstring>
#include<string>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<map>
using namespace std;

#define MAX 3005
#define CLR(arr) memset(arr,0,sizeof(arr))

char str[MAX]; 

double creat(int b,int e)
{
    if(b > e) return 0;
    int p = -1,cnt = 0,flag = 0;
    for(int i = b;i <= e;++i)
    {
        if(str[i] == '(')      cnt++;
        else if(str[i] == ')') cnt--;
        else if((str[i] == '+' || str[i] == '-') && !cnt){flag = 1; p = i;}
        else if((str[i] == '*' || str[i] == '/') && !cnt && !flag)  p = i;
    }
    if(p == -1) 
    {
        if(str[b] <= '9' && str[b] >= '0')
        {
            int res = 0; int n = 0;
            sscanf(&str[b],"%d%n",&res,&n);
            return res;
        }
        return creat(b+1,e-1);
    }
    else 
    {
        switch(str[p])
        {
        case '+':return creat(b,p - 1) + creat(p + 1,e);
        case '-':return creat(b,p - 1) - creat(p + 1,e);
        case '*':return creat(b,p - 1) * creat(p + 1,e);
        case '/':return creat(b,p - 1)*1.0 / creat(p + 1,e);
        default: break;
        }
    }
}

double EXP(char st[])
{
    strcpy(str,st);
    return creat(0,strlen(str)-1); 
}

char ss[2223];
char temp[2223];
void init()
{
    //strcpy(temp,ss);
    int i;
    int add=0;
    for(i=0;ss[i];i++)
    {
        if(ss[i]!=' ')
        {
            temp[add]=ss[i];add++;
        }
    }
    temp[add]=0;
}

int cmp(int a,int b)
{
    return a<b;
}

int a[99];
int main()
{
    int n,m;
    double point;
    while(scanf("%d",&n)!=EOF)
    {
        //init();
        int i,j;
        for(i=1;i<=n;i++){
            scanf("%d",&a[i]);    
        }
        scanf("%lf",&point);
        if(n==0&&point==0)return 0;

        sort(&a[1],&a[n+1],cmp);
        scanf("%s",ss);

        int ok=0;
        do{
            int add=1;
            int j=0;
            for(i=0;ss[i];i++)
            {
                if(ss[i]>='a'&&ss[i]<='z'){
                        if(a[add]>=10)
                        {
                            temp[j]=a[add]/10+'0';j++;
                            temp[j]=a[add]%10+'0';j++;
                        }else
                        {
                            temp[j]=a[add]+'0';j++;
                        }
                        add++;
                }
                else
                {
                    temp[j]=ss[i];j++;
                }
            }
            temp[j]=0;

            //printf("%.2lf\n",EXP(temp));
            if(point==EXP(temp)){
                ok=1;break;
            }
        }while(next_permutation(&a[1],&a[n+1]));
            
        if(ok==0)
            printf("NO\n");
        else
            printf("YES\n");
        //printf("%.2lf\n",EXP(temp));
    }

    return 0;
}