POJ 2965

自己简答的实现了一个队列
* 当push操作的时候,tail++
* 当pop操作的时候,head++

暂时没有考虑队列满和空的情况

#include <iostream>
#include <string.h>
using namespace std;
int visit[1<<16];
int pre[1<<16];
int Q[1<<16];
// first list the mask
int masks[16] = {
        0x111f, 0x222f, 0x444f, 0x888f,
        0x11f1, 0x22f2, 0x44f4, 0x88f8,
        0x1f11, 0x2f22, 0x4f44, 0x8f88,
        0xf111, 0xf222, 0xf444, 0xf888
};
int bfs(int state){
    int head = 0;
    int tail = 0;
    Q[head] = state;
    tail++;
    int step = 0;
    while (tail!=head){
        int t = tail-head;
        for (int i = 0; i < t; ++i) {
            int temp = Q[head++];
            if (temp == 0xffff || step>16)
                return step;
            for (int ix = 0; ix < 16; ++ix) {
                int next = temp^masks[ix];
                if (visit[next] ==-1){
                    Q[tail++] = next;
                    visit[next] = ix;
                    pre[next] = temp;
                }
            }
        }
        step++;
    }
    return -1;
}

int main(){
//    freopen("../in.txt", "r", stdin);
    memset(pre, -1, sizeof(pre));
    memset(visit, -1, sizeof(visit));
    int start = 0;
    int k = 0;
    for (int i = 0; i < 4; ++i) {
        for (int j = 0; j < 4; ++j) {
            char a;
            cin>>a;
            if (a == '-')
                start += (1<<k);
            k++;
        }
    }
    visit[start] = 1;
    pre[start] = -1;
    int ans = bfs(start);
    cout<<ans<<endl;
    if (ans<=16){
        int last = 0xffff;
        while (pre[last]!=-1){
            int a = visit[last];
            cout<<a/4+1<<" "<<a%4+1<<endl;
            last = pre[last];
        }
    }
}