0、题意:求两点之间的最小割的不同的总量
1、分析:裸的分治+最小割,也叫最小割树或GH树,最后用set搞一下就好
#include <set> #include <queue> #include <ctime> #include <cstdio> #include <cstring> #include <cstring> #include <algorithm> using namespace std; #define LL long long #define inf 214748364 struct Edge{ int from, to, cap, flow, next; }; int head[1010], cur[1010]; Edge G[40010]; int tot; int d[1010]; bool vis[1010]; int s, t, n, m; int a[1010]; int b[1010]; inline void init(){ memset(head, -1, sizeof(head)); tot = -1; return; } inline void insert(int from, int to, int cap){ G[++ tot] = (Edge){from, to, cap, 0, head[from]}; head[from] = tot; G[++ tot] = (Edge){to, from, 0, 0, head[to]}; head[to] = tot; return; } inline bool BFS(){ memset(vis, 0, sizeof(vis)); queue<int> Q; Q.push(s); vis[s]=1; d[s]=0; while(!Q.empty()){ int x = Q.front(); Q.pop(); for(int i = head[x]; i != -1; i = G[i].next){ Edge& e = G[i]; if(e.cap - e.flow > 0 && !vis[e.to]){ vis[e.to] = 1; d[e.to]=d[x]+1; Q.push(e.to); } } } return vis[t]; } inline int dfs(int x, int a){ if(x == t || a == 0) return a; int flow = 0, f; for(int& i = cur[x]; i != -1; i = G[i].next){ Edge& e = G[i]; if(d[x]+1 == d[e.to] && (f = dfs(e.to, min(e.cap - e.flow, a))) > 0){ e.flow += f; G[i ^ 1].flow -= f; flow += f; a -= f; if(a == 0) break; } } return flow; } inline int maxflow(){ int res = 0; while(BFS()){ for(int i = 1; i <= n; i ++) cur[i] = head[i]; res += dfs(s, inf); } return res; } inline void DFS(int x){ vis[x] = 1; for(int i = head[x]; i != -1; i = G[i].next) if(!vis[G[i].to] && G[i].cap > G[i].flow){ DFS(G[i].to); } } inline void Clear(){ for(int i = 0; i <= tot; i += 2){ G[i].flow = G[i ^ 1].flow = (G[i].flow + G[i ^ 1].flow) / 2; } } set<int> Set; inline void solve(int l, int r){ if(l == r) return; s = a[l], t = a[r]; Clear(); int tw = maxflow(); Set.insert(tw); int L = l, R = r; for(int i = l; i <= r; i ++){ if(vis[a[i]]) b[L ++] = a[i]; else b[R --] = a[i]; } for(int i = l; i <= r; i ++) a[i] = b[i]; solve(l, L - 1); solve(L, r); } int main(){ scanf("%d%d", &n, &m); init(); for(int i = 1; i <= m; i ++){ int u, v, w; scanf("%d%d%d", &u, &v, &w); insert(u, v, w); insert(v, u, w); } for(int i = 1; i <= n; i ++) a[i] = i; solve(1, n); printf("%d\n", Set.size()); return 0; }