LOJ #2236. 「JLOI2014」松鼠的新家【树上差分】

板子题:

#include 
#include 
#include 
#include 
#include 
#define ll long long
#define rep(i,x,y) for(ll i=(x);i<=(y);i++)
#define repl(i,x,y) for(ll i=(x);i<(y);i++)
#define repd(i,x,y) for(ll i=(x);i>=(y);i--)
using namespace std;

const ll N=3e5+5;
const ll Inf=1e18;

ll n,m,pos[N],sum[N],dep[N],fa[N][20];

ll cnt,to[N<<1],nxt[N<<1],head[N];

inline ll read() {
	ll x=0;char ch=getchar();bool f=0;
	while(ch>'9'||ch<'0'){if(ch=='-')f=1;ch=getchar();}
	while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+ch-'0';ch=getchar();}
	return f?-x:x;
}

void getans(ll x) {
	for(ll i=head[x];i;i=nxt[i]) if(to[i]!=fa[x][0]) getans(to[i]),sum[x]+=sum[to[i]];
}

void ins(ll x,ll y) {
	to[++cnt]=y;nxt[cnt]=head[x];head[x]=cnt;
}

void dfs(ll x) {
	dep[x]=dep[fa[x][0]]+1;
	
	rep(i,1,19) fa[x][i]=fa[fa[x][i-1]][i-1];

	for(ll i=head[x];i;i=nxt[i]) if(to[i]!=fa[x][0]) fa[to[i]][0]=x,dfs(to[i]);
}

ll lca(ll x,ll y) {
	if(dep[x]