HDU 4771 Stealing Harry Potter's Precious

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旅行商问题，状压dp
用一个二进制数表示是否走过当前的几个位置

#include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>#include <string>#include <math.h>#include <stdlib.h>using namespace std;int n,m;char g[110][110];int a[110][110];int sx,sy;int k;int dp[110][110][32];int px[10],py[10];struct Node{    int x,y;    int s;    Node(int _x = 0,int _y = 0,int _s = 0)    {        x = _x;        y = _y;        s = _s;    }};int move_[][2] = {{0,1},{0,-1},{1,0},{-1,0}};int bfs(){    queue<Node>q;    int s = 0;    for(int i = 0;i < k;i++)        if(sx == px[i] && sy == py[i])            s = s|(1<<i);    q.push(Node(sx,sy,s));    memset(dp,-1,sizeof(dp));    dp[sx][sy][s] = 0;    while(!q.empty())    {        Node tmp = q.front();        q.pop();        if(tmp.s == ((1<<k) - 1))        {            return dp[tmp.x][tmp.y][tmp.s];        }        for(int i = 0;i < 4;i++)        {            int nx = tmp.x + move_[i][0];            int ny = tmp.y + move_[i][1];            int s = tmp.s;            if(nx < 0 || nx >= n || ny < 0 || ny >= m)continue;            if(a[nx][ny] == -2)continue;            for(int j = 0;j < k;j++)                if(nx == px[j] && ny == py[j])                {                    s |= (1<<j);                }            if(dp[nx][ny][s] != -1)continue;                dp[nx][ny][s] = dp[tmp.x][tmp.y][tmp.s] + 1;            q.push(Node(nx,ny,s));        }    }    return -1;}int main(){    while(scanf("%d%d",&n,&m) == 2)    {        if(n == 0 && m == 0)break;        for(int i = 0;i < n;i++)            scanf("%s",g[i]);        memset(a,-1,sizeof(a));        for(int i = 0;i < n;i++)            for(int j = 0;j < m;j++)            {                if(g[i][j] == '@')                {                    sx = i;                    sy = j;                }                if(g[i][j] == '#')                    a[i][j] = -2;            }        scanf("%d",&k);        int x,y;        for(int i = 0;i < k;i++)        {            scanf("%d%d",&x,&y);            x --;            y--;            px[i] = x;            py[i] = y;        }        printf("%d\n",bfs());    }    return 0;}

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