POJ 2965

第一次使用位运算

 

其中两个重要的函数，可以加入代码库

 

// get dig from t, right xth
int getDig(int t, int x)
{
    return t>>(x-1)&1;
}
void changeDig(int& t, int x)
{
    t=t^(1<<(x-1));
}

 

用BFS搜，加状态压缩，最多2^16个状态

 

#include <iostream>
#define maxn 65540
#define F(i,a,b) for (int i=a;i<=b;i++)
#include <vector>
using namespace std;
// get dig from t, right xth
int getDig(int t, int x)
{
    return t>>(x-1)&1;
}
void changeDig(int& t, int x)
{
    t=t^(1<<(x-1));
}
int Q[maxn], mk[maxn], f[maxn], l[maxn], r[maxn], now, last, start;
void bfs()
{
    //init
    now=0, last=0;
    Q[++last]=start;
    mk[start]=true;
    while (true)
    {
        int s=Q[++now];
        int temp=s;
        F(i,1,4)
        {
            F(j,1,4)
            {
                int temp=s;
                //ith row
                F(k,0,3)
                    changeDig(temp, 20-4*i-k);
                F(k,0,3)
                    changeDig(temp, 5-j+k*4);
                changeDig(temp, 17-4*(i-1)-j );
                if (!mk[temp])
                {
                    Q[++last]=temp;
                    mk[temp]=true;
                    f[last]=now;
                    l[last]=i;
                    r[last]=j;
                    if (temp==( (1<<16)-1) )
                    {
                        vector<int> v;
                        int k=last, total=0;
                        while (f[k]!=0)
                        {
                            v.push_back(k);
                            k=f[k];
                            total++;
                        }
                        cout << total << endl;
                        vector<int>::iterator it=v.end()-1;
                        cout << l[*it] << " " << r[*it] << endl;
                        while (it!=v.begin() )
                        {
                            it--;
                            cout << l[*it] << " " << r[*it] << endl;
                        }
                        return;
                    }
                }
            }
        }
    }
}
int main()
{
    char ch;
    start=0;
    for (int i=1;i<=16;i++)
    {
        //in
        cin >> ch;
        if (i!=1)
            start<<=1;
        if (ch=='-')
            start++;
    }
    bfs();
    return 0;
}