SGU 536 Berland Chess(状态压缩 + bfs)

在一个n*m的棋盘上，你有一个white king，然后还有一些(<15)个黑子，每个黑子有一定的攻击范围并且他们不会移动。求吃掉所有黑子的最少步数。

黑子的个数很少，所以用状态压缩来表示棋盘上还剩余哪些黑子。在bfs前先要初始化所有黑子状态下的受攻击的点，这个很恶心。。。初始化完了基本就是无脑搜了吧？

#include<algorithm>#include<iostream>#include<cstring>#include<fstream>#include<sstream>#include<cstdlib>#include<vector>#include<string>#include<cstdio>#include<bitset>#include<queue>#include<stack>#include<cmath>#include<map>#include<set>#define FF(i, a, b) for(int i=a; i<b; i++)#define FD(i, a, b) for(int i=a; i>=b; i--)#define REP(i, n) for(int i=0; i<n; i++)#define CLR(a, b) memset(a, b, sizeof(a))#define debug puts("**debug**")#define LL long long#define PB push_back#define MP make_pairusing namespace std;int dwx[8] = {0, 0, 1, -1, 1, 1, -1, -1};int dwy[8] = {1, -1, 0, 0, 1, -1, 1, -1};int dkx[8] = {1, 2, 2, 1, -1, -2, -2, -1};int dky[8] = {2, 1, -1, -2, -2, -1, 1, 2};const int SET = (1<<15);const int maxn = 20;//can[sta][i][j] = 1 : 当前剩余sta中的黑子 点<i, j>不可走//vis[sta][i][j] = 1 ：当前剩余sta中的黑子时，点<i, j>已走过bool can[SET][maxn][maxn], vis[SET][maxn][maxn];char g[maxn][maxn];//id[x][y] ： 点<x, y>的黑子对应的标号int n, m, sx, sy, tot, id[maxn][maxn];inline bool outside(int x, int y){    return x<0 || x>=n || y<0 || y>=m;}//当前剩余sta中的黑子 点x y是否在sta中inline bool has(int sta, int x, int y){    return isalpha(g[x][y]) && (sta & (1<<id[x][y]));}struct Node{    int x, y, st, steps;    Node(){}    Node(int a, int b, int c, int d):x(a), y(b), st(c), steps(d){}};void bfs(){    queue<Node> q; q.push(Node(sx, sy, tot, 0));    vis[tot][sx][sy] = 1;    while(!q.empty())    {        Node T = q.front(); q.pop();        if(T.st == 0)        {            printf("%d\n", T.steps);            return ;        }        REP(i, 8)        {            int tx = T.x + dwx[i], ty = T.y + dwy[i];            if(outside(tx, ty)) continue;            //如果当前状态 包含点<tx, ty>的黑子             if(has(T.st, tx, ty))            {                int sta =  T.st&(tot-(1<<id[tx][ty]));                if(!vis[sta][tx][ty] && !can[sta][tx][ty])                //如果可以吃掉它                {                    q.push(Node(tx, ty, sta, T.steps+1));                    vis[sta][tx][ty] = 1;                }            }            else if(!can[T.st][tx][ty])            {                int sta = T.st;                if(!vis[sta][tx][ty])                {                    q.push(Node(tx, ty, sta, T.steps+1));                    vis[sta][tx][ty] = 1;                }            }        }    }    puts("-1");    return ;}//初始化所有状态下 会被攻击的点void init(){    FF(s, 1, tot+1)    {        //如果s状态下的黑子中 包含g[i][j] 那么更新g[i][j]的攻击范围        REP(i, n) REP(j, m) if(isalpha(g[i][j]) && (s & (1<<id[i][j])))        {                        if(g[i][j] == 'K')            {                REP(k, 8)                {                    int tx = i + dkx[k], ty = j + dky[k];                    if(outside(tx, ty) || has(s, tx, ty)) continue;                    can[s][tx][ty] = 1;                }            }            else if(g[i][j] == 'B')            {                int tx = i, ty = j;                while(true)                {                    tx++, ty++;                    if(outside(tx, ty) || has(s, tx, ty)) break;                    can[s][tx][ty] = 1;                }                tx = i, ty = j;                while(true)                {                    tx--, ty--;                    if(outside(tx, ty) || has(s, tx, ty)) break;                    can[s][tx][ty] = 1;                }                tx = i, ty = j;                while(true)                {                    tx++, ty--;                    if(outside(tx, ty) || has(s, tx, ty)) break;                    can[s][tx][ty] = 1;                }                tx = i, ty = j;                while(true)                {                    tx--, ty++;                    if(outside(tx, ty) || has(s, tx, ty)) break;                    can[s][tx][ty] = 1;                }            }            else            {                int tx = i, ty = j;                while(true)                {                    tx++;                    if(tx >= n || has(s, tx, ty)) break;                    can[s][tx][ty] = 1;                }                tx = i, ty = j;                while(true)                {                    tx--;                    if(tx < 0 || has(s, tx, ty)) break;                    can[s][tx][ty] = 1;                }                tx = i, ty = j;                while(true)                {                    ty++;                    if(ty>=m || has(s, tx, ty)) break;                    can[s][tx][ty] = 1;                }                tx = i, ty = j;                while(true)                {                    ty--;                    if(ty<0 || has(s, tx, ty)) break;                    can[s][tx][ty] = 1;                }            }        }    }}int main(){    scanf("%d%d", &n, &m);    tot = 0;    REP(i, n)    {        scanf("%s", g[i]);        REP(j, m)        {            if(g[i][j] == '*') sx = i, sy = j;            else if(isalpha(g[i][j])) id[i][j] = tot++;        }    }    if(tot == 0)    {        puts("0");        return 0;    }    tot = (1<<tot)-1;    init();         bfs();    return 0;}