spoj 147

dfs枚举真值 

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <stack>

using namespace std;

char s[120];
bool ch[30];
bool b[30];
int cur[30];
int len;
int dfs(int m, int mm)
{
    if(m == mm)
    {
        stack<bool> q;
        for(int i = len-1; i >= 0; i--)
        {
            if(s[i] >= 'a' && s[i] <= 'z')
            {
                q.push(b[cur[s[i]-'a'+1]]);
            }
            else
            {
                if(s[i] == 'C')
                {
                    bool x,y;
                    x = q.top(), q.pop();
                    y = q.top(), q.pop();
                    q.push(x && y);
                }
                else if(s[i] == 'D')
                {
                    bool x,y;
                    x = q.top(), q.pop();
                    y = q.top(), q.pop();
                    q.push(x || y);
                }
                else if(s[i] == 'I')
                {
                    bool x,y;
                    x = q.top(), q.pop();
                    y = q.top(), q.pop();
                    q.push((!x) || y);
                }
                else if(s[i] == 'E')
                {
                    bool x,y;
                    x = q.top(), q.pop();
                    y = q.top(), q.pop();
                    q.push(((!x) || y) && ((!y) || x));
                }
                else
                {
                    bool x;
                    x = q.top(), q.pop();
                    q.push(!x);
                }
            }
        }
        return q.top();
    }
    else
    {
        b[m] = true;
        if(dfs(m+1, mm))
        {
            b[m] = false;
            return dfs(m+1, mm);
        }
    }
    return false;
}
int main()
{
    int n;
    scanf("%d",&n);
    while(n--)
    {
        memset(ch, false, sizeof(ch));
        memset(b, false, sizeof(b));
        scanf("%s",s);
        len = strlen(s);
        for(int i = len-1; i >= 0; i--)
        {
            if(s[i] >= 'a' && s[i] <= 'z')
                ch[s[i] - 'a'+1] = true;
        }
        int e = 1;
        for(int i = 1; i <= 26; i++)
            if(ch[i])
               cur[i] = e++;
        if(dfs(1, e))
            puts("YES");
        else
            puts("NO");
    }
    return 0;
}