模板

STL必背

bool cmpx(re a,re b){return a.x<b.x;}

重载运算符

1.快速幂

while(cnt){
        if(cnt&1)ans=ans*b;
        cnt=cnt>>1;
        b=b*b;
    }

2.矩阵快速幂(yuohua)

3.lca

#include<bits/stdc++.h>
using namespace std;
const int N=1e5+999;
int fa[N][24];
vector<int> v[N];
int n;
void ad(int x,int y){
    v[x].push_back(y);
    v[y].push_back(x);
}
int dep[N],siz[N],zson[N][24];
void dfs(int fath,int x){
    dep[x]=dep[fath]+1;
    fa[x][0]=fath;
    siz[x]=1;
    zson[x][0]=-1;
    int maxer=0;
    for(int i=0;i<v[x].size();i++){
    int dot=v[x][i];
    if(dot!=fath){
        dfs(x,dot);
        siz[x]+=siz[dot];
        if(maxer<siz[dot]){maxer=siz[dot];zson[x][0]=dot;}
    }
    }
}
int lca(int x,int y){
    if(x==y)return x;
    if(dep[x]<dep[y])swap(x,y);
    // X
    for(int i=20;i>=0;i--)
    if(dep[x]-(1<<i)>=dep[y])x=fa[x][i];
    if(x==y)return x;
    if(dep[y]==1)return y;
    for(int i=20;i>=0;i--)
    if(fa[x][i]!=fa[y][i]){x=fa[x][i];y=fa[y][i];}
    return fa[x][0];
}
int q,root;
int main(){
    ios::sync_with_stdio(0);
    freopen("p.in","r",stdin);
    freopen("p.out","w",stdout);
    cin>>n>>q>>root;
    for(int i=1;i<=n-1;i++){
    int a,b;
    cin>>a>>b;
    ad(a,b);
        }
    dfs(0,root);
    for(int i=1;i<=20;i++)
        for(int j=1;j<=n;j++)
        fa[j][i]=fa[fa[j][i-1]][i-1];
    for(int i=1;i<=q;i++){
        int a,b;
        cin>>a>>b;
        cout<<lca(a,b)<<endl;
    }
    return 0;
}

5.system("diff -b -B 1.out 2.out")

6.SET

set<int> s[N];
set<int>::iterator it,it2,it3;

s.begin()
s.end() 
s.insert().first