bzoj 3732（kruskal+LCA）

传送门
题解：先求出MST，然后在跑倍增LCA时顺便维护一个dp数组记录路径上的最大边权。
P.S.WA了好久，因为LCA跳最后一步没取max。。。

#include<cstdio>#include<cstring>#include<iostream>#include<algorithm>using namespace std;const int MAXN=15004;int n,m,q;int head[MAXN],edge=0;struct Kruskal {    int u,v,w;    bool operator <(const Kruskal &s) const {        return w<s.w;    }}d[MAXN<<1];struct EDGE {    int v,nxt,w;}e[MAXN<<1];int fa[MAXN],dis[MAXN],f[16][MAXN],dp[16][MAXN];inline int read() {    int x=0;char c=getchar();    while (c<'0'||c>'9') c=getchar();    while (c>='0'&&c<='9') x=x*10+c-'0',c=getchar();    return x;}inline void adde(int u,int v,int w) {    e[edge].nxt=head[u],e[edge].v=v,e[edge].w=w,head[u]=edge++;    e[edge].nxt=head[v],e[edge].v=u,e[edge].w=w,head[v]=edge++;}void dfs(int p,int father) {    for (int i=head[p];~i;i=e[i].nxt) {        int v=e[i].v;        if (v^father) {            dis[v]=dis[p]+1;            f[0][v]=p;            dp[0][v]=e[i].w;            dfs(v,p);        }    }}inline int find(int x) {    return fa[x]==x?x:fa[x]=find(fa[x]);}void da() {    for (int j=1;(1<<j)<=n;++j)        for (int i=1;i<=n;++i)            f[j][i]=f[j-1][f[j-1][i]],dp[j][i]=max(dp[j-1][i],dp[j-1][f[j-1][i]]);}int lca(int x,int y) {    int mx=0;    if (dis[x]<dis[y]) x^=y^=x^=y;    int t=dis[x]-dis[y];    for (int i=0;i<=14;++i)        if (t&(1<<i)) mx=max(mx,dp[i][x]),x=f[i][x];    if (x==y) return mx;    for (int i=14;~i;--i)        if (f[i][x]^f[i][y]) mx=max(mx,max(dp[i][x],dp[i][y])),x=f[i][x],y=f[i][y];    return max(mx,max(dp[0][x],dp[0][y]));}int main() {//  freopen("bzoj 3732.in","r",stdin);    memset(dp,0,sizeof(dp));    memset(head,-1,sizeof(head));    n=read(),m=read(),q=read();    for (int i=1;i<=n;++i) fa[i]=i;    for (int i=0;i<m;++i) d[i].u=read(),d[i].v=read(),d[i].w=read();    sort(d,d+m);    int cnt=n;    for (int i=0;i<m&&cnt>1;++i) {        int u=d[i].u,v=d[i].v;        int uu=find(u),vv=find(v);        if (uu^vv) {            fa[uu]=vv;            --cnt;            adde(u,v,d[i].w);        }    }    dfs(1,0);    da();    while (q--) {        int u=read(),v=read();        printf("%d\n",lca(u,v));    }    return 0;}