https://codeforces.com/problemset/problem/1304/E
https://codeforces.com/problemset/problem/1304/E
用lca求树上距离
只有3种情况
a->b
a->x+x->y+y->b
a->y+y->x+x->b
因为距离过长就可以来回走,所以k-len得是偶数
#include <iostream> #include <cstdio> #include <cstdlib> #include <algorithm> #include <cmath> #include <cstring> #define inf 2147483647 #define N 1000010 #define p(a) putchar(a) #define For(i,a,b) for(int i=a;i<=b;++i) using namespace std; int n,m,s,x,y,a,b,k; int f[N][21],deep[N]; bool flag; void in(int &x){ int y=1;char c=getchar();x=0; while(c<'0'||c>'9'){if(c=='-')y=-1;c=getchar();} while(c<='9'&&c>='0'){ x=(x<<1)+(x<<3)+c-'0';c=getchar();} x*=y; } void o(int x){ if(x<0){p('-');x=-x;} if(x>9)o(x/10); p(x%10+'0'); } struct node{ int n; node *next; }*e[N]; void push(int x,int y){ node *p; p=new node(); p->n=y; if(e[x]==0) e[x]=p; else{ p->next=e[x]->next; e[x]->next=p; } } void build(int now){ deep[now]=deep[f[now][0]]+1; for(int i=1;(1<<i)<=deep[now];i++) f[now][i]=f[f[now][i-1]][i-1]; for(node *i=e[now];i!=NULL;i=i->next){ if(i->n!=f[now][0]){ f[i->n][0]=now; build(i->n); } } } int query(int x,int y){ if(deep[x]<deep[y]) swap(x,y); int c=deep[x]-deep[y]; for(int i=0;i<=log2(c);i++) if((1<<i)&c) x=f[x][i]; if(x==y) return x; for(int i=log2(deep[x]);i>=0;i--){ if(f[x][i]!=f[y][i]){ x=f[x][i]; y=f[y][i]; } } return f[x][0]; } int l(int x,int y){ return deep[x]+deep[y]-2*deep[query(x,y)]; } int main(){ in(n); For(i,1,n-1){ in(x),in(y); push(x,y); push(y,x); } f[1][0]=1; build(1); in(m); for(int i=1;i<=m;i++){ flag=0; in(x),in(y);in(a);in(b);in(k); if(l(a,b)<=k&&(k-l(a,b))%2==0) flag=1; else if((l(a,x)+1+l(y,b))<=k&&(k-(l(a,x)+1+l(y,b)))%2==0) flag=1; else if((l(a,y)+1+l(x,b))<=k&&(k-(l(a,y)+1+l(x,b)))%2==0) flag=1; if(flag) puts("YES"); else puts("NO"); } return 0; }