HDU 5416 CBR and tree-优快云博客

本文介绍了一种基于深度优先搜索（DFS）的算法实现，用于解决特定类型的图遍历问题。通过递归地访问图中的节点并更新相关数据结构，该算法能够有效地计算出从根节点到每个节点的路径上的异或值，并利用哈希表记录这些值来快速查找互补值。此方法在处理大型图结构时表现出良好的性能。

#include<bits/stdc++.h>
using namespace std;
#define for(i,a,b) for(int i=a;i<=b;++i)

//T,N,Q,,u,v,w,s,tree[maxn][?],val[maxn],cashbook[maxn*2],ans

const int maxn=1e5+5;
struct node
{
    int i,v;
    node(){}
    node(int a,int b){i=a,v=b;}
};
vector<node> tree[maxn];
int val[maxn],cashbook[2*maxn],s;
long long ans;
void dfs(int i,int p)
{
    //record in cashbook[]
    cashbook[val[i]]++;
    //renew ans;
    ans+=cashbook[s^val[i]];
    //move to sons, cal their value
    int nei=tree[i].size();
    for(j,0,nei-1)
    {
        int name=tree[i][j].i;
        if(name==p)continue;
        val[name]=val[i]^tree[i][j].v;
        dfs(name,i);
    }
}
int main()
{
    int T;scanf("%d",&T);
    while(T--)
    {
        //construct the tree
        int N,u,v,w;scanf("%d",&N);
        for(i,1,N)tree[i].clear();
        for(i,1,N-1)
        {
            scanf("%d%d%d",&u,&v,&w);
            tree[u].push_back(node(v,w));
            tree[v].push_back(node(u,w));
        }
        //query
        int Q;scanf("%D",&Q);
        while(Q--)
        {
            memset(cashbook,0,sizeof cashbook);
            memset(val,0,sizeof val);
            ans=0;
            scanf("%d",&s);
            dfs(1,0);
            //print ans
            printf("%lld\n",ans);
        }
    }
}

转载于:https://www.cnblogs.com/maoruimas/p/9585666.html