【SCOI 2005】 骑士精神

【题目链接】

            https://www.lydsy.com/JudgeOnline/problem.php?id=1085

【算法】

           IDA*

【代码】

           

#include<bits/stdc++.h>
using namespace std;
const int dx[8] = {-2,-2,-1,-1,1,1,2,2};
const int dy[8] = {-1,1,-2,2,-2,2,-1,1};
const int goal[5][5] = 
{    
{1,1,1,1,1},
{0,1,1,1,1},
{0,0,2,1,1},
{0,0,0,0,1},
{0,0,0,0,0} 
};

int i,j,T,x,y,step;
char c;
bool solved;
int mp[5][5];

inline bool valid(int x,int y)
{
        return x >= 0 && x < 5 && y >= 0 && y < 5;
}
inline int f()
{
        int i,j;
        int ret = 0;
        for (i = 0; i < 5; i++)
        {
                for (j = 0; j < 5; j++)
                {
                        if (mp[i][j] != goal[i][j])
                                ret++;        
                }    
        }        
        return ret - 1;
}

inline bool IDDFS(int dep,int x,int y)
{
        int i,tx,ty;
        if (dep + f() > step) return false;
        if (dep == step) return true;
        for (i = 0; i < 8; i++)
        {
                tx = x + dx[i];
                ty = y + dy[i];
                if (valid(tx,ty))
                {
                        swap(mp[x][y],mp[tx][ty]);
                        if (IDDFS(dep+1,tx,ty)) return true;
                        swap(mp[x][y],mp[tx][ty]);
                }
        }
        return false;
}

int main() 
{
        
        scanf("%d",&T);
        getchar();
        while (T--)
        {
                solved = false;
                for (i = 0; i < 5; i++)
                {
                        for (j = 0; j < 5; j++)
                        {
                                c = getchar();
                                if (c == '0')    mp[i][j] = 0;
                                else if (c == '1') mp[i][j] = 1;
                                else 
                                {
                                        x = i;
                                        y = j;
                                        mp[i][j] = 2;    
                                }
                        }    
                        getchar();
                }    
                for (i = 0; i <= 15; i++)
                {
                        step = i;
                        if (IDDFS(0,x,y))    
                        {
                                printf("%d\n",i);
                                solved = true;
                                break;
                        }
                }    
                if (!solved) printf("-1\n");
        }
        
        return 0;
    
}