P2762 太空飞行计划问题 最大权闭合子图
link:https://www.luogu.org/problemnew/show/P2762
题意
承担实验赚钱,但是要花去对应仪器的费用,仪器可能共用。
求最大的收益和对应的选择方案。
思路
这道题读入有点技巧,就是要自己判断换行
这道题和费用流关系不大,是最大权闭合子图,源点连接实验,容量为收益,实验向对应的仪器连接容量为inf的边,仪器向汇点连接容量为费用的边。
跑出最小割s,即最大流,然后用实验总收益 - s即可。
至于如何输出方案,即输出最大权闭合子图中的点。就是跑最后一次bfs的时候,有dis的点就是选中的点。
结合图形我们可以这么理解,从源点流到实验的边一定不能流满,要是满了,就说明这个做这个实验没有任何意义。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#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 boost \ ios::sync_with_stdio(false); \ cin.tie(0) #define rep(a, b, c) for (int a = (b); a <= (c); ++a) #define max3(a, b, c) max(max(a, b), c); #define min3(a, b, c) min(min(a, b), c); const ll oo = 1ll << 17; const ll mos = 0x7FFFFFFF; //2147483647 const ll nmos = 0x80000000; //-2147483648 const int inf = 0x3f3f3f3f; const ll inff = 0x3f3f3f3f3f3f3f3f; //18 const int mod = 1e9 + 7; const double esp = 1e-8; 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 = 0; int f = 0; char ch = getchar(); while (ch < '0' || ch > '9') f |= (ch == '-'), ch = getchar(); while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar(); return x = f ? -x : x; } inline void cmax(int &x, int y) { if (x < y) x = y; } inline void cmax(ll &x, ll y) { if (x < y) x = y; } inline void cmin(int &x, int y) { if (x > y) x = y; } inline void cmin(ll &x, ll y) { if (x > y) x = y; } /*-----------------------showtime----------------------*/ const int maxn = 1e4 + 9; struct E { int u, v, w; int nxt; } edge[maxn]; int gtot = 0, head[maxn]; void addedge(int u, int v, int w) { edge[gtot].u = u; edge[gtot].v = v; edge[gtot].w = w; edge[gtot].nxt = head[u]; head[u] = gtot++; edge[gtot].u = v; edge[gtot].v = u; edge[gtot].w = 0; edge[gtot].nxt = head[v]; head[v] = gtot++; } int dis[maxn], cur[maxn]; bool bfs(int s, int t) { rep(i, s, t) cur[i] = head[i]; memset(dis, inf, sizeof(dis)); dis[s] = 0; queue<int> que; que.push(s); while (!que.empty()) { int u = que.front(); que.pop(); for (int i = head[u]; ~i; i = edge[i].nxt) { int v = edge[i].v, w = edge[i].w; if (w > 0 && dis[v] > dis[u] + 1) { dis[v] = dis[u] + 1; que.push(v); } } } return dis[t] < inf; } int dfs(int u, int t, int maxflow) { if (u == t || maxflow == 0) return maxflow; for (int i = cur[u]; ~i; i = edge[i].nxt) { cur[u] = i; int v = edge[i].v, w = edge[i].w; if (w > 0 && dis[v] == dis[u] + 1) { int f = dfs(v, t, min(w, maxflow)); if (f > 0) { edge[i].w -= f; edge[i ^ 1].w += f; return f; } } } return 0; } int dinic(int s, int t) { int flow = 0; while (bfs(s, t)) { while (int f = dfs(s, t, inf)) flow += f; } return flow; } char tools[10000]; int init[maxn]; int main() { memset(head, -1, sizeof(head)); int n, m; scanf("%d%d", &n, &m); int s = 0, t = n + m + 1; int sum = 0; for (int i = 1; i <= n; i++) { int x; scanf("%d", &x); addedge(s, i, x); init[i] = x; sum += x; memset(tools, 0, sizeof tools); cin.getline(tools, 10000); int ulen = 0, tool; //之前已经用scanf读完了赞助商同意支付该实验的费用 //tool是该实验所需仪器的其中一个 //这一行,你可以将读进来的编号进行储存、处理,如连边。 while (sscanf(tools + ulen, "%d", &tool) == 1) { addedge(i, n + tool, inf); // cout<<tool<<endl; if (tool == 0) ulen++; else { while (tool) { tool /= 10; ulen++; } } ulen++; } } for (int i = 1; i <= m; i++) { int x; scanf("%d", &x); addedge(i + n, t, x); init[i + n] = x; } int ans = sum - dinic(s, t); for (int i = 1; i <= n; i++) { if (dis[i] < inf) printf("%d ", i); } puts(""); for (int i = 1; i <= m; i++) { if (dis[i + n] < inf) printf("%d ", i); } puts(""); printf("%d\n", ans); return 0; }
skr