bzoj 1085: [SCOI2005]骑士精神 IDA*

题目链接

给一个图， 目标位置是确定的， 问你能否在15步之内达到目标位置。

因为只有15步， 所以直接ida*

#include<bits/stdc++.h>
using namespace std;
#define pb(x) push_back(x)
#define ll long long
#define mk(x, y) make_pair(x, y)
#define lson l, m, rt<<1
#define mem(a) memset(a, 0, sizeof(a))
#define rson m+1, r, rt<<1|1
#define mem1(a) memset(a, -1, sizeof(a))
#define mem2(a) memset(a, 0x3f, sizeof(a))
#define rep(i, a, n) for(int i = a; i<n; i++)
#define ull unsigned long long
typedef pair<int, int> pll;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int mod = 1e9+7;
const int inf = 1061109567;
const int dir[][2] = { {-1, 2}, {1, 2}, {2, -1}, {2, 1},{-1,-2},{-2,-1},{-2,1},{1,-2} };
int ans[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 a[5][5], flag;
int judge() {
    for(int i = 0; i<5; i++) {
        for(int j = 0; j<5; j++) {
            if(a[i][j]!=ans[i][j])
                return 0;
        }
    }
    return 1;
}
int h() {
    int ret = 0;
    for(int i = 0; i<5; i++) {
        for(int j = 0; j<5; j++) {
            if(ans[i][j]!=a[i][j])
                ret++;
        }
    }
    return ret;
}
int step;
int dfs(int d) {
    if(d==step)
        return judge();
    for(int i = 0; i<5; i++) {
        for(int j = 0; j<5; j++) {
            if(a[i][j] == 2) {
                for(int k = 0; k<8; k++) {
                    int x = i+dir[k][0];
                    int y = j+dir[k][1];
                    if(x<0||x>4||y<0||y>4)
                        continue;
                    swap(a[i][j], a[x][y]);
                    if(d+h()<=step)
                         if(dfs(d+1))
                            return 1;
                    swap(a[i][j], a[x][y]);
                }
            }
        }
    }
    return 0;
}
int main()
{
    int t;
    cin>>t;
    char s[6];
    while(t--) {
        for(int i = 0; i<5; i++) {
            scanf("%s", s);
            for(int j = 0; j<5; j++) {
                if(s[j] == '*')
                    a[i][j] = 2;
                else
                    a[i][j] = s[j]-'0';
            }
        }
        flag = 0;
        for(int i = 0; i<=15; i++) {
            step = i;
            if(dfs(0)) {
                printf("%d\n", i);
                flag = 1;
                break;
            }
        }
        if(!flag)
            cout<<"-1"<<endl;
    }
    return 0;
}