codevs 3372 选学霸(hash+并查集+多重背包)

来源：互联网发布：mac中page up 编辑：程序博客网时间：2024/06/01 08:48

先通过并查集处理出来有多少种不同的集合，每个集合有多少人。一定要不要忘记了与别的没有联系的独立点。

并查集的时候可以通过hash处理出来每个数目相同的集合的个数。

这样以人数为权值，个数为限制进行多重背包，结果就是答案。

题目链接：http://codevs.cn/problem/3372/

#include <algorithm>#include <iostream>#include <stdlib.h>#include <string.h>#include <iomanip>#include <stdio.h>#include <string>#include <queue>#include <cmath>#include <stack>#include <map>#include <set>#define eps 1e-8#define M 1000100#define LL long long//#define LL long long#define INF 0x3f3f3f#define PI 3.1415926535898#define mod 1000000007const int maxn = 30010;using namespace std;int vis1[maxn];int vis2[maxn];int vis[maxn];int num[maxn];int dp[2*maxn];int fa[maxn];struct node{    int snum;    int sum;} p[maxn];int n;void init(){    for(int i = 0; i <= n; i++) fa[i] = i;    memset(vis1, 0, sizeof(vis1));    memset(vis2, 0, sizeof(vis2));    memset(dp, 0, sizeof(dp));    memset(vis, 0, sizeof(vis));}int Find(int x){    if(x != fa[x]) fa[x] = Find(fa[x]);    return fa[x];}void add(int x, int y){    int x1, y1;    x1 = Find(x);    y1 = Find(y);    if(x1 != y1) fa[x1] = y1;}int main(){    int m, k;    while(~scanf("%d %d %d",&n, &m, &k))    {        init();        int x, y;        for(int i = 0; i < k; i++)        {            scanf("%d %d",&x, &y);            vis[x] = 1;            vis[y] = 1;            add(x, y);        }        int ans = 0;        int xsum = 0;        for(int i = 1; i <= n; i++)        {            if(!vis[i])            {                xsum ++;                continue;            }            int s = Find(i);            vis1[s] ++;        }        for(int i = 1; i <= n; i++)        {            if(!vis1[i]) continue;            num[ans++] = vis1[i];        }        sort(num, num+ans);        for(int i = 0; i < ans; i++) vis2[num[i]]++;        int cnt = 0;        for(int i = 1; i <= n; i++)        {            if(!vis2[i]) continue;            p[cnt].snum = i;            p[cnt++].sum = vis2[i];        }        int v = 2*(m+1);        dp[0] = 1;        for(int i = 0; i < cnt; i++)        {            for(int j = v; j >= 0; j--)            {                if(!dp[j]) continue;                for(int kk = 1; kk <= p[i].sum; kk++)                {                    if(kk*p[i].snum+j > v) break;                    if(dp[kk*p[i].snum+j]) break;                    dp[kk*p[i].snum+j] = 1;                }            }        }        int lx, rx;        for(int i = m; i >= 0; i--)        {            if(dp[i])            {                lx = i;                break;            }        }        for(int i = m; i <= 2*(m+1); i++)        {            if(dp[i])            {                rx = i;                break;            }        }        lx = max(lx, 0);        rx = min(rx, 2*(m+1));        int sx = abs(m-lx);        int sy = abs(rx-m);        if(sx <= xsum)        {            sx = 0;            lx = m;        }        else        {            sx -= xsum;            lx += xsum;        }        if(sy < sx)        {            cout<<rx<<endl;            continue;        }        cout<<lx<<endl;    }    return 0;}/*10 4 98 21 55 109 710 33 44 68 96 805 3 31 22 33 44*/

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