luogu3379 最近公共祖先（LCA） tarjan 倍增

来源：互联网发布：数据采集技术有哪些编辑：程序博客网时间：2024/06/07 05:33

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tarjan不多言

#include <iostream>#include <cstdio>using namespace std;struct Edge{    int too, nxt;}edge[1000005];struct Ques{    int nxt, too, ran;}ques[1000005];int getint(){    char ch=getchar();    int re=0;    while(ch<'0' || ch>'9')    ch = getchar();    while(ch>='0' && ch<='9'){        re = re*10 + ch - '0';        ch = getchar();    }    return re;}int n, m, ecnt, qcnt, ehea[500005], qhea[500005], fa[500005], uu, vv;int s, ans[500005];bool vis[500005];void add_edge(int fro, int too){    edge[++ecnt].nxt = ehea[fro];    edge[ecnt].too = too;    ehea[fro] = ecnt;}void add_ques(int fro, int too, int ran){    ques[++qcnt].nxt = qhea[fro];    ques[qcnt].too = too;    ques[qcnt].ran = ran;    qhea[fro] = qcnt;}int myfind(int x){    return fa[x]==x?x:fa[x]=myfind(fa[x]);}void tarjan(int u){    vis[u] = true;    for(int i=ehea[u]; i; i=edge[i].nxt){        int t=edge[i].too;        if(!vis[t]){            tarjan(t);            fa[t] = u;        }    }    for(int i=qhea[u]; i; i=ques[i].nxt){        int t=ques[i].too;        if(vis[t])            ans[ques[i].ran] = myfind(t);    }}int main(){    n = getint();    m = getint();    s = getint();    for(int i=1; i<n; i++){        uu = getint();        vv = getint();        add_edge(uu, vv);        add_edge(vv, uu);        fa[i] = i;    }    fa[n] = n;    for(int i=1; i<=m; i++){        uu = getint();        vv = getint();        add_ques(uu, vv, i);        add_ques(vv, uu, i);    }    tarjan(s);    for(int i=1; i<=m; i++)        printf("%d\n", ans[i]);    return 0;}

倍增亦不多言

#include <iostream>#include <cstdio>using namespace std;int n, m, s, grand[500005][22], deep[500005], hea[500005], cnt, uu, vv;struct Edge{    int too, nxt;}edge[1000005];int getint(){    char ch=getchar();    int re=0;    while(ch<'0' || ch>'9') ch = getchar();    while(ch>='0' && ch<='9'){        re = re*10 + ch - '0';        ch = getchar();    }    return re;}void add_edge(int fro, int too){    edge[++cnt].nxt = hea[fro];    edge[cnt].too = too;    hea[fro] = cnt;}void builddepth(int u){    for(int i=hea[u]; i; i=edge[i].nxt){        int t=edge[i].too;        if(!deep[t]){            deep[t] = deep[u] + 1;            grand[t][0] = u;            builddepth(t);        }    }}void init(){    deep[s] = 1;    builddepth(s);    for(int i=1; i<=19; i++)        for(int j=1; j<=n; j++)            grand[j][i] = grand[grand[j][i-1]][i-1];}int getlca(int x, int y){    if(deep[x]<deep[y]){        x ^= y;        y ^= x;        x ^= y;    }    for(int i=19; i>=0; i--)        if(deep[grand[x][i]]>=deep[y])            x = grand[x][i];    if(x==y)    return x;    for(int i=19; i>=0; i--)        if(grand[x][i]!=grand[y][i]){            x = grand[x][i];            y = grand[y][i];        }    return grand[x][0];}int main(){    n = getint();    m = getint();    s = getint();    for(int i=1; i<n; i++){        uu = getint();        vv = getint();        add_edge(uu, vv);        add_edge(vv, uu);    }    init();    for(int i=1; i<=m; i++){        uu = getint();        vv = getint();        printf("%d\n", getlca(uu, vv));    }    return 0;}

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