这题和3358一模一样,建模形式直接不用变,就两点不一样,一是len变化了,加入y后再更新即可,还有就是可能会出现x0=x1的情况,即一条开线段垂直x轴,如果我们依旧按照上一题的建图方法,就会出现负权环,无法跑出答案,我们就可以把一个点拆成入点和出点,这样无论是否是不是垂直都可以一样建,注意开long long,不开long long可能只有9分
#include<bits/stdc++.h> using namespace std; #define lowbit(x) ((x)&(-x)) #define sqr(x) ((x)*(x)) typedef long long LL; const int maxm = 1e5+5; const LL INF = 0x3f3f3f3f3f3f3f3f; struct edge{ LL u, v, cap, flow, cost, nex; } edges[maxm]; struct Points{ LL l, r, len; } point[505]; LL head[maxm], cur[maxm], cnt, fa[1024<<1], n, d[1024<<1], allx[1024]; bool inq[1024<<1]; void init() { memset(head, -1, sizeof(head)); } void add(int u, int v, LL cap, LL cost) { edges[cnt] = edge{u, v, cap, 0, cost, head[u]}; head[u] = cnt++; } void addedge(int u, int v, LL cap, LL cost) { add(u, v, cap, cost), add(v, u, 0, -cost); } bool spfa(int s, int t, int &flow, LL &cost) { for(int i = 0; i <= n+2; ++i) d[i] = INF; //init() memset(inq, false, sizeof(inq)); d[s] = 0, inq[s] = true; fa[s] = -1, cur[s] = INF; queue<int> q; q.push(s); while(!q.empty()) { int u = q.front(); q.pop(); inq[u] = false; for(int i = head[u]; i != -1; i = edges[i].nex) { edge& now = edges[i]; int v = now.v; if(now.cap > now.flow && d[v] > d[u] + now.cost) { d[v] = d[u] + now.cost; fa[v] = i; cur[v] = min(cur[u], now.cap - now.flow); if(!inq[v]) {q.push(v); inq[v] = true;} } } } if(d[t] == INF) return false; flow += cur[t]; cost += 1LL*d[t]*cur[t]; for(int u = t; u != s; u = edges[fa[u]].u) { edges[fa[u]].flow += cur[t]; edges[fa[u]^1].flow -= cur[t]; } return true; } int MincostMaxflow(int s, int t, LL &cost) { cost = 0; int flow = 0; while(spfa(s, t, flow, cost)); return flow; } void run_case() { init(); LL l, r, y1, y2; int k, xcnt = 0; cin >> n >> k; for(int i = 1; i <= n; ++i) { cin >> l >> y1 >> r >> y2; LL tmp = 1LL*floor(sqrt(sqr(r-l)+sqr(y2-y1))); if(l > r) swap(l, r); l <<= 1, r <<= 1; if(l == r) r|=1; else l|=1; allx[++xcnt] = l, allx[++xcnt] = r, point[i] = Points{l, r, tmp}; } sort(allx+1,allx+1+xcnt); int len = unique(allx+1,allx+1+xcnt)-allx; for(int i = 1; i <= n; ++i) { point[i].l = lower_bound(allx+1,allx+len,point[i].l)-allx; point[i].r = lower_bound(allx+1,allx+len,point[i].r)-allx; } for(int i = 1; i < len-1; ++i) addedge(i, i+1, INF, 0); int s = 0, t = len; for(int i = 1; i <= n; ++i) { addedge(point[i].l, point[i].r, 1, -point[i].len); } addedge(s, 1, k, 0), addedge(len-1, t, k, 0); LL cost = 0; n = len; MincostMaxflow(s, t, cost); cout << -cost; } int main() { ios::sync_with_stdio(false), cin.tie(0); run_case(); cout.flush(); return 0; }
原文地址:https://www.cnblogs.com/GRedComeT/p/12288375.html
时间: 2024-11-09 02:46:05