POJ - 1741 - Tree - 点分治模板

题意：

对于带权的一棵树，求树中距离不超过k的点的对数。

思路：

点分治的裸题。　将这棵树分成很多小的树，分治求解。

#include <algorithm>

#include  <iterator>

#include  <iostream>

#include   <cstring>

#include   <cstdlib>

#include   <iomanip>

#include    <bitset>

#include    <cctype>

#include    <cstdio>

#include    <string>

#include    <vector>

#include     <cmath>

#include     <queue>

#include      <list>

#include       <map>

#include       <set>

using namespace std;

//#pragma GCC optimize(3)

//#pragma comment(linker, "/STACK:102400000,102400000")  //c++

#define lson (l , mid , rt << 1)

#define rson (mid + 1 , r , rt << 1 | 1)

#define debug(x) cerr << #x << " = " << x << "\n";

#define pb push_back

#define pq priority_queue

typedef long long ll;

typedef unsigned long long ull;

typedef pair<ll ,ll > pll;

typedef pair<int ,int > pii;

typedef pair<int,pii> p3;

//priority_queue<int> q;//这是一个大根堆q

//priority_queue<int,vector<int>,greater<int> >q;//这是一个小根堆q

#define fi first

#define se second

//#define endl '\n'

#define OKC ios::sync_with_stdio(false);cin.tie(0)

#define FT(A,B,C) for(int A=B;A <= C;++A)  //用来压行

#define REP(i , j , k)  for(int i = j ; i <  k ; ++i)

//priority_queue<int ,vector<int>, greater<int> >que;

const ll mos = 0x7FFFFFFFLL;  //

const ll nmos = 0x80000000LL;  //-2147483648

const int inf = 0x3f3f3f3f;

const ll inff = 0x3f3f3f3f3f3f3f3fLL; //

const int mod = ;

const double PI=acos(-1.0);

// #define _DEBUG;         //*//

#ifdef _DEBUG

freopen("input", "r", stdin);

// freopen("output.txt", "w", stdout);

#endif

/*-----------------------showtime----------------------*/

            const int maxn = 1e5+;

            int root = ,S,mx;

            int n,k;

            int sz[maxn],f[maxn],dis[maxn],cnt;

            bool used[maxn];

            struct node

            {

                int to,w,nx;

            }e[maxn];

            int h[maxn],tot = ;

            void add(int u,int v,int w){

                e[tot].to = v;

                e[tot].w = w;

                e[tot].nx = h[u];

                h[u] = tot++;

            }

            void getRoot(int u, int fa){

                sz[u] = ,f[u] = ;

                for(int i = h[u] ; ~i; i= e[i].nx){

                    int v = e[i].to;

                    if(used[v] || fa == v)continue;

                    getRoot(v,u);

                    sz[u] += sz[v];

                    f[u] = max(f[u] , sz[v]);

                }

                f[u] = max(f[u],S - sz[u]);

                if(f[u] < mx){root = u;mx = f[u];}

            }

            void getDis(int u,int fa,int D){

                for(int i=h[u] ; ~i; i=e[i].nx){

                    int v = e[i].to;

                    if(used[v]||v == fa)continue;

                    dis[++cnt] = D + e[i].w;

                    getDis(v,u,dis[cnt]);

                }

            }

            int getAns(int x,int D){

                dis[cnt = ] = D;

                getDis(x,,D);

                sort(dis+,dis++cnt);

                int le = ,ri =cnt,ans = ;

                while(le <= ri){

                    if(dis[le] + dis[ri] <= k)ans += ri - le,le++;

                    else ri--;

                }

                return ans;

            }

            int Divide(int x){

                used[x] = true;

                ll ans = getAns(x,);

                for(int i=h[x]; ~i; i= e[i].nx){

                    int v = e[i].to;

                    if(used[v])continue;

                    ans -= getAns(v,e[i].w);

                    mx = inf,S = sz[v];

                    getRoot(v,x);ans += Divide(root);

                }

                return ans;

            }

int main(){

            while(~scanf("%d%d", &n, &k) && n+k)

            {

                memset(h,-,sizeof(h));

                memset(used,false,sizeof(used));

                tot = ;

                for(int i=; i<n; i++){

                    int u,v,c;

                    scanf("%d%d%d", &u, &v,&c);

                    add(u,v,c);

                    add(v,u,c);

                }

                S = n;mx = inf;

                getRoot(,-);

                printf("%d\n",Divide(root));

            }

            return ;

}

POJ-1741

自己今天又写了一遍。

//点分治

//#pragma GCC optimize(3)

//#pragma comment(linker, "/STACK:102400000,102400000")  //c++

// #pragma GCC diagnostic error "-std=c++11"

// #pragma comment(linker, "/stack:200000000")

// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

// #pragma GCC optimize("-fdelete-null-pointer-checks,inline-functions-called-once,-funsafe-loop-optimizations,-fexpensive-optimizations,-foptimize-sibling-calls,-ftree-switch-conversion,-finline-small-functions,inline-small-functions,-frerun-cse-after-loop,-fhoist-adjacent-loads,-findirect-inlining,-freorder-functions,no-stack-protector,-fpartial-inlining,-fsched-interblock,-fcse-follow-jumps,-fcse-skip-blocks,-falign-functions,-fstrict-overflow,-fstrict-aliasing,-fschedule-insns2,-ftree-tail-merge,inline-functions,-fschedule-insns,-freorder-blocks,-fwhole-program,-funroll-loops,-fthread-jumps,-fcrossjumping,-fcaller-saves,-fdevirtualize,-falign-labels,-falign-loops,-falign-jumps,unroll-loops,-fsched-spec,-ffast-math,Ofast,inline,-fgcse,-fgcse-lm,-fipa-sra,-ftree-pre,-ftree-vrp,-fpeephole2",3)

#include <algorithm>

#include  <iterator>

#include  <iostream>

#include   <cstring>

#include   <cstdlib>

#include   <iomanip>

#include    <bitset>

#include    <cctype>

#include    <cstdio>

#include    <string>

#include    <vector>

#include     <stack>

#include     <cmath>

#include     <queue>

#include      <list>

#include       <map>

#include       <set>

#include   <cassert>

using namespace std;

#define lson (l , mid , rt << 1)

#define rson (mid + 1 , r , rt << 1 | 1)

#define debug(x) cerr << #x << " = " << x << "\n";

#define pb push_back

#define pq priority_queue

typedef long long ll;

typedef unsigned long long ull;

//typedef __int128 bll;

typedef pair<ll ,ll > pll;

typedef pair<int ,int > pii;

typedef pair<int,pii> p3;

//priority_queue<int> q;//这是一个大根堆q

//priority_queue<int,vector<int>,greater<int> >q;//这是一个小根堆q

#define fi first

#define se second

//#define endl '\n'

#define OKC ios::sync_with_stdio(false);cin.tie(0)

#define FT(A,B,C) for(int A=B;A <= C;++A)  //用来压行

#define REP(i , j , k)  for(int i = j ; i <  k ; ++i)

#define max3(a,b,c) max(max(a,b), c);

#define min3(a,b,c) min(min(a,b), c);

//priority_queue<int ,vector<int>, greater<int> >que;

const ll mos = 0x7FFFFFFF;  //

const ll nmos = 0x80000000;  //-2147483648

const int inf = 0x3f3f3f3f;

const ll inff = 0x3f3f3f3f3f3f3f3f; //

const int mod = 1e9+;

const double esp = 1e-;

const double PI=acos(-1.0);

const double PHI=0.61803399;    //黄金分割点

const double tPHI=0.38196601;

template<typename T>

inline T read(T&x){

    x=;int f=;char ch=getchar();

    while (ch<''||ch>'') f|=(ch=='-'),ch=getchar();

    while (ch>=''&&ch<='') x=x*+ch-'',ch=getchar();

    return x=f?-x:x;

}

/*-----------------------showtime----------------------*/

/*

using namespace std;

#define pb push_back

#define debug(x) cerr<<#x<<" = " << x<<endl;

#define fi first

#define se second

typedef pair<int,int> pii;

const int inf = 0x3f3f3f3f;

*/

        int n,k,ans;

        const int maxn = ;

        vector<pii>mp[maxn];

        int dp[maxn],cen[maxn];

        void getsize(int u,int fa){

            dp[u] = ;

            for(int i=; i<mp[u].size(); i++){

                int v = mp[u][i].fi;

                if(fa == v || cen[v]) continue;

                getsize(v, u);

                dp[u] += dp[v];

            }

        }

        pii getbig(int u,int fa,int t){

            pii res = pii(inf, u);

            int mx = ;

            for(int i=; i<mp[u].size(); i++){

                int v = mp[u][i].fi;

                if(v == fa || cen[v])continue;

                res = min(res, getbig(v, u, t));

                mx = max(mx, dp[v]);

            }

            res = min(res, pii(max(mx, t - dp[u]), u));

            return res;

        }

        void dfs(int u,int fa,int c, vector<int> & b){

            b.pb(c);

            for(int i=; i<mp[u].size(); i++){

                int v = mp[u][i].fi,d = c + mp[u][i].se;

                if(v == fa || cen[v])continue;

                dfs(v,u,d,b);

            }

        }

        int cal(vector<int>&b){

            sort(b.begin(), b.end());

            int res = ,r = b.size();

            for(int i=; i<b.size(); i++){

                while(r && b[i] + b[r-] > k) r--;

                if(r > i) res += r - ;

                else res += r;

            }

            return res/;

        }

        void solve(int u){

            getsize(u, -);

            int s = getbig(u, -,dp[u]).se;

            cen[s] = ;

            for(int i=; i<mp[s].size(); i++){

                int v = mp[s][i].fi;

                if(cen[v])continue;

                solve(v);

            }

            vector<int>a;

            a.pb();

            for(int i=; i<mp[s].size(); i++)

            {

                int v = mp[s][i].fi;

                if(cen[v])continue;

                vector<int>b;

                dfs(v, s, mp[s][i].se, b);

                ans -= cal(b);

                a.insert(a.end(),b.begin(),b.end());

            }

            ans += cal(a);

            cen[s] = ;

        }

int main(){

        while(~scanf("%d%d", &n, &k) && n + k){

            for(int i=; i<=n; i++) mp[i].clear();

            for(int i=; i<n; i++){

                int u,v,w;

                scanf("%d%d%d", &u, &v, &w);

                mp[u].pb(pii(v,w));

                mp[v].pb(pii(u,w));

            }

            ans = ;

            solve();

            printf("%d\n", ans);

        }

        return ;

}

new

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POJ - 1741 - Tree - 点分治模板

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POJ - 1741 - Tree - 点分治 模板

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POJ - 1741 - Tree - 点分治模板