省选_简单算法

这里是一些简单的算法模板，没有编译过.（编译过的话会做特殊说明）

目录：

 1.最近公共祖先

 2.CDQ分治

1.最近公共祖先

namespace LCA{
    #define LOG 21 
    int cnt; 
    int f[22][maxn],dep[maxn];
    int head[maxn],to[maxn],nex[maxn]; 
    void addedge(int u,int v){
        nex[++cnt] = head[u],head[u]=cnt,to[cnt] = v; 
    }
    void dfs(int u,int fa){
        dep[u] = dep[fa] + 1; 
        f[0][u]=fa; 
        for(int i=1;i<LOG;++i) f[i][u]=f[i-1][f[i-1][u]]; 
        for(int i=head[u];i;i=nex[i])
            if(to[i]!=fa)dfs(to[i],u); 
    }
    int query(int x,int y){
        if(dep[x]<dep[y]) swap(x,y); 
        if(dep[x]!=dep[y]){
            for(int i=LOG-1;i>=0;--i) 
                if(dep[f[i][y]]<=dep[x]) y=f[i][y]; 
        }
        if(x==y) return x; 
        for(int i=LOG-1;i>=0;--i)
            if(f[i][x]!=f[i][y])
                x=f[i][x],y=f[i][y]; 
        return f[0][x]; 
    }
}; 

　

2.CDQ分治（二维 LIS）

//CDQ分治 --- 3维LIS
namespace CDQ{
    #define maxn 500060 
    #define ll long long 
    #define nex (oo = (oo * A) % mod)
    #define setIO(s) freopen(s".in","r",stdin) 
    int n,cnt,fin,ans[maxn]; 
    long long mod,oo = 1,A,H[maxn]; 
    void getmax(int &a,int b){ if(b > a) a = b; }
    struct Node{
        long long x,y,z; 
        int id; 
    }node[maxn],arr[maxn]; 
    int cmpx(Node a,Node b){ 
        if(a.x == b.x && a.y == b.y) return a.z < b.z; 
        if(a.x == b.x) return a.y < b.y; 
        return a.x < b.x;  
    }
    int cmpy(Node a,Node b){
        if(a.x == b.x) return a.y < b.y; 
        return a.x < b.x; 
    }
    int equal(Node a,Node b) {
        return (a.x == b.x && a.y == b.y && a.z == b.z); 
    }
    struct BIT{
        int C[maxn]; 
        int lowbit(int x){
            return x & (-x); 
        }
        void update(int p,int x){
            while(p < maxn){
                C[p] = max(C[p],x); 
                p += lowbit(p); 
            }
        }
        int query(int p){
            if(p <= 0) return 0; 
            int ss = 0;
            while(p > 0) {
                ss = max(ss,C[p]), p -= lowbit(p); 
            }
            return ss; 
        }
        void del(int p){
            while(p < maxn) C[p] = 0,p += lowbit(p); 
        }
    }tree;
    void solve(int l,int r){
        if(l >= r) return ;
        int mid = (l + r) >> 1,tl = l,tr = mid + 1;
        solve(l,mid); 
        sort(arr+l,arr+mid+1,cmpy),sort(arr+mid+1,arr+r+1,cmpy); 
        while(tl <= mid && tr <= r){
            if(arr[tl].y < arr[tr].y){
                tree.update(arr[tl].z,ans[arr[tl].id]); 
                ++tl; 
            }
            else {
                getmax(ans[arr[tr].id],tree.query(arr[tr].z - 1) + 1); 
                ++tr; 
            }
        }
        for(int i = tr;i <= r; ++i) getmax(ans[arr[i].id],tree.query(arr[i].z-1) + 1); 
        for(int i = l;i <= mid; ++i) tree.del(arr[i].z); 
        sort(arr+mid+1,arr+1+r,cmpx),solve(mid+1,r); 
    }; 
};