4242: 水壶

题目链接

题目大意：矩阵，有建筑物，原野，墙壁，走原野需要1单位水，建筑物可以补满水，多次询问两个建筑物间需要携带的水壶大小

题解：平面图上的最小生成树，然后就是货车运输了

Orz题解

我的收获：

#include<iostream>#include<cstdio>#include<cstring>#define N 2005#define M 200005using namespace std; int n,m,pt,cas,tot,cnt,fa[M][18],g[M][18],bin[25],anc[M],fst[M],pnt[N*N],nxt[N*N],len[N*N];int dep[M],h[N*N][2],d[N][N],blg[N][N]; bool mp[N][N];const int dx[4]={-1,1,0,0},dy[4]={0,0,-1,1};int read(){    int x=0; char ch=getchar();    while (ch<'0' || ch>'9') ch=getchar();    while (ch>='0' && ch<='9'){ x=x*10+ch-'0'; ch=getchar(); }    return x;}struct grapg{    int fst[N*N];    void add(int x,int y,int z){        pnt[++tot]=y; nxt[tot]=fst[x]; len[tot]=z; fst[x]=tot;    }}g1,g2;int getanc(int x){ return (x==anc[x])?x:anc[x]=getanc(anc[x]); }void dfs(int x){    int p,i;    for (i=1; bin[i]<=dep[x]; i++){        fa[x][i]=fa[fa[x][i-1]][i-1];        g[x][i]=max(g[x][i-1],g[fa[x][i-1]][i-1]);    }    for (p=g2.fst[x]; p; p=nxt[p]){        int y=pnt[p];        if (y!=fa[x][0]){            fa[y][0]=x; g[y][0]=len[p];            dep[y]=dep[x]+1; dfs(y);        }    }}int qry(int x,int y){    if (getanc(x)!=getanc(y)) return -1;    if (dep[x]<dep[y]) swap(x,y); int tmp=dep[x]-dep[y],i,ans=0;    for (i=0; bin[i]<=tmp; i++)        if (tmp&bin[i]){ ans=max(ans,g[x][i]); x=fa[x][i]; }    for (i=17; i>=0; i--)        if (fa[x][i]!=fa[y][i]){            ans=max(ans,max(g[x][i],g[y][i]));            x=fa[x][i]; y=fa[y][i];        }    if (x!=y) ans=max(ans,max(g[x][0],g[y][0])); return ans;}int main(){    m=read(); n=read(); pt=read(); cas=read();    int i,j; char ch=getchar();    bin[0]=1; for (i=1; i<=18; i++) bin[i]=bin[i-1]<<1;    for (i=1; i<=m; i++){        while (ch!='.' && ch!='#') ch=getchar();        for (j=1; j<=n; j++,ch=getchar())            mp[i][j]=(ch=='.');    }    int head=0,tail=0,x,y,z;    memset(d,-1,sizeof(d));    for (i=1; i<=pt; i++){        h[++tail][0]=x=read(); h[tail][1]=y=read();        blg[x][y]=i; d[x][y]=0;        anc[i]=i;    }    while (head<tail){        x=h[++head][0]; y=h[head][1]; z=blg[x][y];        for (i=0; i<4; i++){            int u=x+dx[i],v=y+dy[i];            if (u>0 && u<=m && v>0 && v<=n && mp[u][v])                if (d[u][v]==-1){                    d[u][v]=d[x][y]+1; blg[u][v]=z;                    h[++tail][0]=u; h[tail][1]=v;                } else if (z!=blg[u][v]) g1.add(d[u][v]+d[x][y],z,blg[u][v]);        }    }    for (i=0; i<m*n; i++)        for (j=g1.fst[i]; j; j=nxt[j]){            x=getanc(pnt[j]); y=getanc(len[j]);            if (x!=y){                anc[x]=y; g2.add(pnt[j],len[j],i);                g2.add(len[j],pnt[j],i);            }        }    for (i=1; i<=pt; i++)        if (getanc(i)==i){            dep[i]=1; dfs(i);        }    while (cas--) printf("%d\n",qry(read(),read()));    return 0;}