• HDU 4308 Saving Princess claire_(简单BFS)


    求出不使用P点时起点到终点的最短距离,求出起点到所有P点的最短距离,求出终点到所有P点的最短距离。

    答案=min( 不使用P点时起点到终点的最短距离, 起点到P的最短距离+终点到P的最短距离 )

    #include <cstdio>
    #include <cstring>
    #include <cstdlib>
    #include <algorithm>
    #include <queue>
    
    using namespace std;
    
    const int MAXN = 5100;
    const int INF  = 1 << 30;
    
    const int dx[] = { -1,  0, 0, 1 };
    const int dy[] = {  0, -1, 1, 0 };
    
    struct node
    {
        int x, y;
        int cost;
        int id;
        bool operator<( const node &rhs ) const
        {
            return cost < rhs.cost;
        }
    };
    
    int R, C, cost;
    char mat[MAXN][MAXN];
    bool vis[MAXN][MAXN];
    int  index[MAXN][MAXN];
    int G[2][MAXN/10];
    node P[MAXN/10], start, end;
    int cntP;
    
    void init( )
    {
        cntP = 1;
        for ( int i = 0; i < R; ++i )
            for ( int j = 0; j < C; ++j )
            {
                if ( mat[i][j] == 'P' )
                {
                    P[cntP].x = i;
                    P[cntP].y = j;
                    P[cntP].cost = 0;
                    P[cntP].id = cntP;
                    //printf( "cntP=%d [%d, %d]
    ", cntP, i, j );
                    ++cntP;
                }
                else if ( mat[i][j] == 'Y' )
                {
                    start.x = i;
                    start.y = j;
                    start.cost = 0;
                }
                else if ( mat[i][j] == 'C' )
                {
                    end.x = i;
                    end.y = j;
                    end.cost = 0;
                }
            }
    
        P[0] = start;
        P[0].id = 0;
    
        P[cntP] = end;
        P[cntP].id = cntP;
        //printf( "cntP = %d
    ", cntP );
        for ( int i = 0; i <= cntP; ++i )
            index[ P[i].x ][ P[i].y ] = i;
        return;
    }
    
    bool check( int x, int y )
    {
        if ( x >= 0 && x < R && y >= 0 && y < C ) return true;
        return false;
    }
    
    int BFS( int c, node st )
    {
        for ( int i = 0; i < R; ++i )
        for ( int j = 0; j < C; ++j )
            vis[i][j] = false;
    
        queue<node> Q;
    
        st.cost = 0;
        vis[ st.x ][ st.y ] = true;
        Q.push(st);
    
        while ( !Q.empty() )
        {
            node cur = Q.front();
            Q.pop();
    
            for ( int i = 0; i < 4; ++i )
            {
                int xx = cur.x + dx[i];
                int yy = cur.y + dy[i];
                if ( check( xx, yy ) && mat[xx][yy] != '#' && !vis[xx][yy] )
                {
                    node next;
                    next.x = xx;
                    next.y = yy;
                    next.cost = cur.cost;
                    next.id = index[xx][yy];
                    if ( mat[xx][yy] != '*' )
                    {
                        int id = index[xx][yy];
                        G[c][id] = next.cost;
                    }
                    else
                        next.cost += cost;
    
                    vis[xx][yy] = true;
                    Q.push(next);
                }
            }
        }
        return INF;
    }
    
    int getG()
    {
        //printf("***cntP=%d
    ", cntP);
        for ( int i = 0; i <= cntP; ++i )
        {
            G[0][i] = INF;
            G[1][i] = INF;
        }
    
        BFS( 0, P[0] );
        BFS( 1, P[cntP] );
    
        int ans = G[0][cntP];
        //printf("***ans=%d
    ", ans );
    
        for ( int i = 1; i < cntP; ++i )
            for ( int j = 1; j < cntP; ++j )
            {
                if ( G[0][i] < INF && G[1][j] < INF )
                    ans = min( ans, G[0][i] + G[1][j] );
                //printf( "ans = %d
    ", ans );
            }
    
        return ans;
    }
    
    int main()
    {
        while ( scanf( "%d%d%d", &R, &C, &cost ) == 3 )
        {
            for ( int i = 0; i < R; ++i )
                scanf( "%s", mat[i] );
    
            init();
            int ans = getG();
    
            if ( ans < INF ) printf( "%d
    ", ans );
            else puts("Damn teoy!");
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/GBRgbr/p/3588433.html
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