HDU-4280 Island Transport (ISAP)

HDU-4280 Island Transport (ISAP)

You are required to send tourists from the eastmost to the westmost. the edge is bidirectional and there is no difference.

Solution: bare stream

ISAP 8080 MS

#include 
  
   #include 
   
    #include #include 
    
     #include 
     
      using namespace std;#define N 100010#define INF 0x3f3f3f3fstruct Edge {    int from, to, cap, flow;    Edge() {}    Edge(int from, int to, int cap, int flow): from(from), to(to), cap(cap), flow(flow) {}};struct ISAP {    int p[N], num[N], cur[N], d[N];    int t, s, n, m;    bool vis[N];    vector
      
        G[N]; vector
       
         edges; void init(int n) { this->n = n; for (int i = 0; i <= n; i++) { G[i].clear(); d[i] = INF; } edges.clear(); } void AddEdge(int from, int to, int cap) { edges.push_back(Edge(from, to, cap, 0)); edges.push_back(Edge(to, from, 0, 0)); m = edges.size(); G[from].push_back(m - 2); G[to].push_back(m - 1); } bool BFS() { memset(vis, 0, sizeof(vis)); queue
        
          Q; d[t] = 0; vis[t] = 1; Q.push(t); while (!Q.empty()) { int u = Q.front(); Q.pop(); for (int i = 0; i < G[u].size(); i++) { Edge &e = edges[G[u][i] ^ 1]; if (!vis[e.from] && e.cap > e.flow) { vis[e.from] = true; d[e.from] = d[u] + 1; Q.push(e.from); } } } return vis[s]; } int Augment() { int u = t, flow = INF; while (u != s) { Edge &e = edges[p[u]]; flow = min(flow, e.cap - e.flow); u = edges[p[u]].from; } u = t; while (u != s) { edges[p[u]].flow += flow; edges[p[u] ^ 1].flow -= flow; u = edges[p[u]].from; } return flow; } int Maxflow(int s, int t) { this->s = s; this->t = t; int flow = 0; BFS(); if (d[s] >= n) return 0; memset(num, 0, sizeof(num)); memset(cur, 0, sizeof(cur)); for (int i = 0; i < n; i++) if (d[i] < INF) num[d[i]]++; int u = s; while (d[s] < n) { if (u == t) { flow += Augment(); u = s; } bool ok = false; for (int i = cur[u]; i < G[u].size(); i++) { Edge &e = edges[G[u][i]]; if (e.cap > e.flow && d[u] == d[e.to] + 1) { ok = true; p[e.to] = G[u][i]; cur[u] = i; u = e.to; break; } } if (!ok) { int Min = n - 1; for (int i = 0; i < G[u].size(); i++) { Edge &e = edges[G[u][i]]; if (e.cap > e.flow) Min = min(Min, d[e.to]); } if (--num[d[u]] == 0) break; num[d[u] = Min + 1]++; cur[u] = 0; if (u != s) u = edges[p[u]].from; } } return flow; }};ISAP isap;int n, m;void init() { scanf(%d%d, &n, &m); isap.init(n); int x, y; int Min = INF, Max = -INF; int s, t; for (int i = 1; i <= n; i++) { scanf(%d%d, &x, &y); if (x <= Min) { s = i; Min = x; } if (x >= Max) { t = i; Max = x; } } int u, v, c; for (int i = 0; i < m; i++) { scanf(%d%d%d, &u, &v, &c); isap.AddEdge(u, v, c); isap.AddEdge(v, u, c); } int ans = isap.Maxflow(s, t); printf(%d, ans);}int main() { int test; scanf(%d, &test); while (test--) { init(); } return 0;}