BZOJ#1085[SCOI2005]骑士精神

[SCOI2005]骑士精神

思路：

迭代加深，启发式剪枝

代码：

#include <bits/stdc++.h>
#define int long long
int _ = 0, Case = 1;
using namespace std;
#define all(v) begin(v),end(v)
#define nline '\n'
const int N = 10;
int d[N][N];
int a[N][N];
int b[N][N];
void init() {
    for (int i = 1; i <= 5; i++) {
        for (int j = 1; j <= 5; j++) {
            d[i][j] = 1;
        }
    }
    for (int i = 2; i <= 5; i++) {
        for (int j = 1; j <= i; j++) {
            d[i][j] = 0;
        }
    }
    d[2][2] = 1;
    d[3][3] = 2;
}
int dx[] = {1, 1, 2, 2, -2, -2, -1, -1};
int dy[] = {2, -2, 1, -1, 1, -1, 2, -2};
int check() {
    int cnt = 0;
    for (int i = 1; i <= 5; i++) {
        for (int j = 1; j <= 5; j++) {
            cnt += (b[i][j] != d[i][j]);
        }
    }
    return cnt;
}
bool dfs(int x, int y, int cur, int depth) {
    int t = check();
    if (!t) return true;
    if (cur - 1 + t > depth) return false;
    for (int i = 0; i < 8; i++) {
        int tx = dx[i] + x, ty = y + dy[i];
        if (tx >= 1 and tx <= 5 and ty >= 1 and ty <= 5) {
            swap(b[x][y], b[tx][ty]);
            if (dfs(tx, ty, cur + 1, depth)) return true;
            swap(b[x][y], b[tx][ty]);
        }
    }
    return false;
}
void solve(int Case) {
    int x, y;
    for (int i = 1; i <= 5; i++) {
        for (int j = 1; j <= 5; j++) {
            char ch;
            cin >> ch;
            if (ch == '*') {
                x = i, y = j;
                a[i][j] = 2;

            } else {
                a[i][j] = ch - '0';
            }
        }
    }
    memcpy(b, a, sizeof b);
    for (int i = 0; i <= 15; i++) {
        if (dfs(x, y, 0, i)) {
            cout << i << nline;
            return;
        }
        memcpy(b, a, sizeof b);
    }
    cout << -1 << nline;
}

signed main() {
    init();
    ios::sync_with_stdio(false); cin.tie(nullptr);
    cin >> _; for (Case = 1; Case <= _; Case++)
        solve(Case);

    return 0;
}