HDU 1429 胜利大逃亡(续)（状压bfs）

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与其他bfs不同的是这种题需要用二进制来保存钥匙这个状态，需要多用一维数组来保存。。

可以通过位运算 | “拾取钥匙”， & “匹配钥匙”。

#include "string"#include "iostream"#include "cstdio"#include "cmath"#include "set"#include "queue"#include "vector"#include "cctype"#include "sstream"#include "cstdlib"#include "cstring"#include "stack"//#include "ctime"#include "algorithm"#define pa pair<int,int>#define Pi M_PI#define INF 0x3f3f3f3f#define INFL 0x3f3f3f3f3f3f3f3fLLusing namespace std;typedef long long LL;const int M=55;struct Node{    int x, y;    int kind;    int t;} star;int n, m, time;int dis[4][2] = {1, 0, 0, -1, -1, 0, 0, 1};char map[21][21];bool mark[20][20][1100];int BFS(){    int i, j, kind, temp, t;    struct Node node, next;    queue<Node> Q;    star.kind = 0;    star.t = 0;    Q.push(star);    mark[star.x][star.y][0] = true;    while(!Q.empty())    {        node = Q.front();        Q.pop();        kind = node.kind;        t = node.t;        if( t % time == 0 && t != 0)        {            node.x = star.x;            node.y = star.y;        }        if( map[node.x][node.y] == '^')            return node.t;        for( i = 0 ; i < 4 ; i++)        {            next.x = node.x + dis[i][0];            next.y = node.y + dis[i][1];            next.kind = kind;            if( next.x < 0 || next.y < 0 || next.x >= n || next.y >= m)                continue;            if( map[next.x][next.y] == '*' || mark[next.x][next.y][next.kind] == true)                continue;            next.t = t + 1;            if( islower(map[next.x][next.y]))            {                j = map[next.x][next.y] - 'a';                if( (kind & (1 << j) ) == 0)  //存储钥匙                    next.kind = kind + (1 << j);            }            else if( isupper( map[next.x][next.y]) )            {                j = map[next.x][next.y] - 'A';                temp = kind >> j;                if( (temp & 1 ) == 0)    //判断钥匙能匹配不                    continue;                next.kind = kind;            }            mark[next.x][next.y][next.kind] = true;            Q.push(next);        }    }    return -1;}int main(){    int i, j, k, ans;    k = 0;    while(~ scanf("%d%d%d", &n, &m, &time))    {        memset( mark, 0, sizeof(mark));        for( i = 0 ; i < n ; i++)            {                for( j = 0 ; j < m ; j++)                {                    cin>>map[i][j];                    if( map[i][j] == '@')                    {                        star.x=i;                        star.y=j;                    }               }           }        ans = BFS();        printf("%d\n", ans);    }}

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