题意：
就是求最小割点
解析：
正向一遍spfa 反向一遍spfa 然后遍历每一条边，对于当前边 如果dis1[u] + dis2[v] + 1 <= k 那么就把这条边加入到网络流图中，
每个点拆点 边权为1
跑最大流即可
代码还是改的那一题。。。
#include#include #include #include #include #include #define mem(a,b) memset(a,b,sizeof(a))using namespace std;const int maxn = 1e3 + 10, INF = 0xfffffff, maxm = 100010;typedef long long LL;int n,m, cnt, s, t, k;int head[maxn], d[maxn], vis[maxn], dis1[maxn], dis2[maxn], head1[maxn], cur[maxn];int from[maxm], to[maxm];int bz[55][55], way[55][55];struct edge{ int u, v, c, next;}Edge[maxm << 1];void add_(int u, int v, int c){ Edge[cnt].u = u; Edge[cnt].v = v; Edge[cnt].c = c; Edge[cnt].next = head1[u]; head1[u] = cnt++;}void add_edge(int u, int v, int c){ add_(u, v, c); add_(v, u, 0);}bool bfs(){ mem(d, 0); queue Q; Q.push(s); d[s] = 1; while(!Q.empty()) { int u = Q.front(); Q.pop(); for(int i = head1[u]; i != -1; i = Edge[i].next) { edge e = Edge[i]; if(!d[e.v] && e.c > 0) { d[e.v] = d[u] + 1; Q.push(e.v); if(e.v == t) return 1; } } } return d[t] != 0;}int dfs(int u, int cap){ int ret = 0; if(u == t || cap == 0) return cap; for(int &i = cur[u]; i != -1; i = Edge[i].next) { edge e = Edge[i]; if(d[e.v] == d[u] + 1 && e.c > 0) { int V = dfs(e.v, min(e.c, cap)); Edge[i].c -= V; Edge[i ^ 1].c += V; ret += V; cap -= V; if(cap == 0) break; } } if(cap > 0) d[u] = -1; return ret;}int Dinic(){ int ans = 0; while(bfs()) { memcpy(cur, head1, sizeof(head1)); ans += dfs(s, INF); } return ans;}struct node{ int u, v, w, next;}Node[maxn * 10];void add(int u,int v,int w,int i){ Node[i].u = u; Node[i].v = v; Node[i].w = w; Node[i].next = head[u]; head[u] = i;}void spfa(int s){ for(int i = 0; i < maxn; i++) d[i] = INF; queue Q; d[s] = 0; mem(vis,0); Q.push(s); vis[s] = 1; while(!Q.empty()) { int u = Q.front();Q.pop(); vis[u] = 0; for(int i=head[u]; i!=-1; i=Node[i].next) { node e = Node[i]; if(d[e.v] > d[u] + e.w) { d[e.v] = d[u] + e.w; if(!vis[e.v]) { Q.push(e.v); vis[e.v] = 1; } } } }}int main(){ int T,A,B; while(~scanf("%d%d%d", &n, &m, &k)) { if(n==0&&m==0&&k==0) break; mem(way, 0); mem(bz, 0); mem(Node,0); mem(head,-1); mem(head1, -1); cnt = 0; for(int i=0; i