[BeiJing wc2012]连连看

题目链接 费用流板子+拆点

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
inline int read()
{
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}


/********************************************************************/

struct ZKM_MinCostMaxFlow{
    const static int maxn = 1e5+50;
    const static int maxE = 1e5+50;
    const static int INF = 0xfffffff;

    struct Edge{
        int to, next, cap, flow, cost;
        Edge(int _to = 0, int _next = 0, int _cap = 0, int _flow = 0, int _cost = 0):
            to(_to), next(_next), cap(_cap), flow(_flow), cost(_cost){}
    }edge[maxE*2];

    int head[maxn], tot;
    int cur[maxn], dis[maxn];
    bool vis[maxn];
    int ss, tt, N;
    int min_cost, max_flow;
    void init(int N){
        tot = 0;
        for(int i = 0;i < N;i++) head[i] = -1;
    }
    int addedge(int u, int v, int cap, int cost){
        edge[tot] = Edge(v, head[u], cap, 0, cost);
        int rs = tot;
        head[u] = tot++;
        edge[tot] = Edge(u, head[v], 0, 0, -cost);
        head[v] = tot++;
        return rs;
    }
    int aug(int u, int flow){
        if(u == tt) return flow;
        vis[u] = true;
        for(int i = cur[u];i != -1;i = edge[i].next){
            int v = edge[i].to;
            if(edge[i].cap > edge[i].flow && !vis[v] && dis[u] == dis[v] + edge[i].cost){
                int tmp = aug(v, min(flow, edge[i].cap - edge[i].flow));
                edge[i].flow += tmp;
                edge[i^1].flow -= tmp;
                cur[u] = i;
                if(tmp) return tmp;
            }
        }
        return 0;
    }
    bool modify_label(){
        int d = INF;
        for(int u = 0;u < N;u++){
            if(vis[u]){
                for(int i = head[u];i != -1;i = edge[i].next){
                    int v = edge[i].to;
                    if(edge[i].cap > edge[i].flow && !vis[v]){
                        d = min(d, dis[v]+edge[i].cost - dis[u]);
                    }
                }
            }
        }
        if(d == INF) return false;
        for(int i = 0;i < N;i++){
            if(vis[i]){
                vis[i] = false;
                dis[i] += d;
            }
        }
        return true;
    }

    pair<int, int> mincostmaxflow(int start, int ed, int n){
        ss = start, tt = ed, N = n;
        min_cost = max_flow = 0;
        for(int i = 0;i < n;i++) dis[i] = 0;
        while(1){
            for(int i = 0;i < n;i++) cur[i] = head[i];
            while(1){
                for(int i = 0;i < n;i++) vis[i] = false;
                int tmp = aug(ss, INF);
                if(tmp == 0) break;
                max_flow += tmp;
                min_cost += tmp*dis[ss];
            }
            if(!modify_label()) break;
        }
        return make_pair( max_flow, min_cost );
    }
}solver;

int gcd(int x, int y){
    if(y == 0) return x;
    else return gcd(y, x%y);
}

bool check(int x, int y){
    if(x == y) return false;
    if(x < y)  swap(x, y);
    int t = sqrt(x*x-y*y);
    if(t*t != x*x-y*y) return false;
    if(gcd(y, t) != 1) return false;
    return true;
}

int main(){
    int a, b;
    a = read(); b = read();
    solver.init(b*2+5);
    for(int i = a;i <= b;i++){
        for(int j = a;j <= b;j++){
            if(check(i, j)){
                solver.addedge(i, j+b, 1, -i-j);
            }
        }
        solver.addedge(b*2+1, i, 1, 0);     //拆点
        solver.addedge(i+b, b*2+2, 1, 0);   //拆点
    }
    pair<int, int> ans = solver.mincostmaxflow(b*2+1, b*2+2, b*2+5);
    printf("%d %d
", ans.first/2, -ans.second/2);
    return 0;
}