P2324 [SCOI2005]骑士精神(迭代加深+dfs)

迭代加深

• 在限定的步数内，进行最优化剪枝。
• 一般题给都会给出限定条件。

P2324 [SCOI2005]骑士精神

#include <bits/stdc++.h>
#define INF 0x3f3f3f3f
#define DOF 0x7f7f7f7f
#define endl '
'
#define mem(a, b) memset(a, b, sizeof(a))
#define debug(case, x) cout << case << "  : " << x << endl
#define open freopen("ii.txt", "r", stdin)
#define close freopen("oo.txt", "w", stdout)
#define IO                       
    ios::sync_with_stdio(false); 
    cin.tie(0);                  
    cout.tie(0)
#define pb push_back
using namespace std;
//#define int long long
#define lson rt << 1
#define rson rt << 1 | 1
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<long long, long long> PII;
const int maxn = 1e6 + 10;


int a[7][7], t[7][7] = {
    {0},
    {0, 1, 1, 1, 1, 1},
    {0, 0, 1, 1, 1, 1},
    {0, 0, 0, -1, 1, 1},
    {0, 0, 0, 0, 0, 1},
    {0, 0, 0, 0, 0, 0}
};
int d = 0, dir[8][2] = {
    {1, 2}, {1, -2}, {-1, 2}, {-1, -2},
    {2, 1}, {2, -1}, {-2, 1}, {-2, -1}
};


int gtg(){
    int res=0;
    for(int i=1;i<=5;++i){
        for(int j=1;j<=5;++j){
            if(a[i][j]!=t[i][j])++res;
        }
    }
    return res;
}

bool dfs(int x,int y,int dep){
    int tmp=gtg();
    if(tmp+dep>d+1) return false;
    if(!tmp)return true;
    for(int i=0;i<8;++i){
        int xx=x+dir[i][0],yy=y+dir[i][1];
        if(x>=1&&x<=5&&y>=1&&y<=5){
            swap(a[x][y],a[xx][yy]);
            if(dfs(xx,yy,dep+1)) return true;
            swap(a[x][y],a[xx][yy]);
        }
    }
    return false;
}

void solve() {
    int x, y;
    for(int i = 1; i <= 5; ++i) {
        string str;
        cin >> str;
        for(int j = 1; j <= 5; ++j) {
            if(str[j - 1] == '*')a[i][j] = -1, x = i, y = j;
            else a[i][j]=str[j-1]-'0';
        }
    }

    for(d = 0; d<=15;++d){
        if(dfs(x,y,0)){
            cout<<d<<endl;
            return ;
        }
    }
    cout<<-1<<endl;

}


int main() {
    int t;
    cin >> t;
    while(t--) {
        solve();
    }

}