A ARK

E Everspace

F Fallout

H Halo

異或知識+tries樹

計算從根節點到每個點的異或距離，再從中找出兩個異或後值最大的即可。

#include<cstring>
#include<cstdio>
#include<algorithm>
#define maxn 100100
using namespace std;
typedef long long ll;
struct node
{
    int to,nxt,w;
}e[maxn*2];
int num,last[maxn],ch[maxn*32][2],cnt;
ll f[maxn],note[maxn
 
*32];
void add(int x,int y,int z)
{
    e[++num].to=y;
    e[num].nxt=last[x];
    last[x]=num;
    e[num].w=z;
}

void build(ll now)
{
    int i,u=0,x;
    for (i=31;i>=0;i--)
    {
        x=(now>>i)&1;
        if (!ch[u][x]) ch[u][x]=++cnt;
        u=ch[u][x];
    }
    note[u]=now;
}
ll find(ll now)
{
    
 
int i,u=0,x;
    for (i=31;i>=0;i--)
    {
        x=(now>>i)&1;
        if (ch[u][x^1]) u=ch[u][x^1];
        else u=ch[u][x];
    }
    return note[u];
}
void dfs(int fa,int x)
{
    for (int i=last[x];i!=-1;i=e[i].nxt)
    {
        if (e[i].to==fa) continue;
        f[e[i].to]=f[x]^e[i].w;
        dfs(x,e[i].to);
    }
}
 
int main()
{
    int n,x,y,z,i;
    ll tmp,ans;
    while (scanf("%d",&n)!=EOF)
    {
        memset(last,-1,sizeof(last));
        memset(f,0,sizeof(f));
        memset(ch,0,sizeof(ch));
        memset(note,0,sizeof(note));
        num=0;cnt=0;ans=0;
        for (i=1;i<n;i++)
        {
            scanf("%d%d%d",&x,&y,&z);
            add(x,y,z);
            add(y,x,z);
        }
        build(0);
        dfs(0,0);
        for (i=0;i<n;i++) build(f[i]);
        for (i=0;i<n;i++)
        {
            tmp=find(f[i])^f[i];
            if (tmp>ans) ans=tmp;
        }
        printf("%lld\n",ans);
    }
    return 0;
}

I Icey

J Just Cause

K Kerbal Space Program