洛谷P2324 [SCOI2005]骑士精神

题目链接：

kmakma!

题目分析：

启发式搜索入门经典题

• 迭代加深：
  本题最大次数15次，超过15次直接return
• 估价函数：
  当前走的次数和与答案的偏差值，超过16直接return

代码：

#include <bits/stdc++.h>
using namespace std;
inline int read() {
	int cnt = 0, f = 1; char c = getchar();
	while (!isdigit(c)) {if (c == '-') f = -f; c = getchar();}
	while (isdigit(c)) {cnt = (cnt << 3) + (cnt << 1) + c - '0'; c = getchar();}
	return cnt * f;
}
const char check[10][10] = 
{{'1', '1', '1', '1', '1'},
 {'0', '1', '1', '1', '1'},
 {'0', '0', '*', '1', '1'},
 {'0', '0', '0', '0', '1'},
 {'0', '0', '0', '0', '0'}};
const int dx[10] = {1, -1, 1, -1, 2, -2, 2, -2};
const int dy[10] = {2, -2, -2, 2, 1, -1, -1, 1};
char mapp[10][10];
int T, ans;
int spacex, spacey;
int test() {
	int tot = 0;
	for (register int i = 0; i < 5; i++)
		for (register int j = 0; j < 5; j++)
			if (mapp[i][j] != check[i][j]) ++tot;
//	cout<<tot<<endl;
	return tot;
}
void dfs_(int cnt, int x, int y, int lastx, int lasty) {
//	cout<<x<<" "<<y<<endl;
	if (cnt + test() > 16) return;
	if (cnt >= ans) return;
	if (!test()) {ans = min(ans, cnt); return;}
	for (register int i = 0; i <= 7; ++i) {
			if (x + dx[i] < 0 || x + dx[i] > 4) continue;
			if (y + dy[i] < 0 || y + dy[i] > 4) continue;
			if (x + dx[i] == lastx && y + dy[i] == lasty) continue;
				swap(mapp[x + dx[i]][y + dy[i]], mapp[x][y]);
				dfs_(cnt + 1, x + dx[i], y + dy[i], x, y);
				swap(mapp[x + dx[i]][y + dy[i]], mapp[x][y]);
	}
}
int main() {
	T = read();
	while (T--) {
		ans = 10000;
		memset(mapp, 0, sizeof(mapp));
		for (register int i = 0; i < 5; ++i) scanf("%s", mapp[i]);
		for (register int i = 0; i < 5; ++i)
			for (register int j = 0; j < 5; ++j)
				if (mapp[i][j] == '*') spacex = i, spacey = j;
		dfs_(0, spacex, spacey, -1, -1);
		ans == 10000 ? printf("-1
") : printf("%d
", ans);
	}
	return 0;
}