【HDOJ】2209 翻纸牌游戏

状态压缩+双向广搜。注意控制时间t。

/* 2209 */
#include <iostream>
#include <string>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#include <deque>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <climits>
#include <cctype>
#include <cassert>
#include <functional>
using namespace std;
//#pragma comment(linker,"/STACK:102400000,1024000")

#define sti                set<int>
#define stpii            set<pair<int, int> >
#define mpii            map<int,int>
#define vi                vector<int>
#define pii                pair<int,int>
#define vpii            vector<pair<int,int> >
#define rep(i, a, n)     for (int i=a;i<n;++i)
#define per(i, a, n)     for (int i=n-1;i>=a;--i)
#define clr                clear
#define pb                 push_back
#define mp                 make_pair
#define fir                first
#define sec                second
#define all(x)             (x).begin(),(x).end()
#define SZ(x)             ((int)(x).size())
#define lson            l, mid, rt<<1
#define rson            mid+1, r, rt<<1|1

const int maxn = 1<<20;
bool mark1[maxn+5];
bool mark2[maxn+5];
char s[25];
int m[25];

void init() {
    m[0] = 1;
    rep(i, 1, 25)
        m[i] = m[i-1]<<1;
}

void bfs() {
    queue<int> Q1, Q2;
    int x = 0, xx;
    int i, j, k;
    int t = 0;

    memset(mark1, false, sizeof(mark1));
    memset(mark2, false, sizeof(mark2));

    for (i=0; s[i]; ++i)
        x = (x<<1) + s[i]-‘0‘;

    if (x == 0) {
        puts("0");
        return ;
    }

    int l = i;
    Q1.push(x);
    mark1[x] = true;
    Q2.push(0);
    mark2[0] = true;
    int sz1, sz2;

    while (!Q1.empty() && !Q2.empty()) {
        ++t;

        sz1 = SZ(Q1);
        while (sz1--) {
            x = Q1.front();
            Q1.pop();
            for (i=0; i<l; ++i) {
                xx = x;
                xx ^= m[i];
                if (i)
                    xx ^= m[i-1];
                if (i+1 < l)
                    xx ^= m[i+1];
                if (mark1[xx])
                    continue;
                if (mark2[xx]) {
                    printf("%d\n", t+t-1);
                    return ;
                }
                mark1[xx] = true;
                Q1.push(xx);
            }
        }

        sz2 = SZ(Q2);
        while (sz2--) {
            x = Q2.front();
            Q2.pop();
            for (i=0; i<l; ++i) {
                xx = x;
                xx ^= m[i];
                if (i)
                    xx ^= m[i-1];
                if (i+1 < l)
                    xx ^= m[i+1];
                if (mark2[xx])
                    continue;
                if (mark1[xx]) {
                    printf("%d\n", t+t);
                    return ;
                }
                mark2[xx] = true;
                Q2.push(xx);
            }
        }
    }

    puts("NO");
}

int main() {
    ios::sync_with_stdio(false);
    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
        freopen("data.out", "w", stdout);
    #endif

    init();
    while (scanf("%s", s)!=EOF) {
        bfs();
    }

    #ifndef ONLINE_JUDGE
        printf("time = %d.\n", (int)clock());
    #endif

    return 0;
}