标签:sub void bfs other pre string cas white time
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#include <iostream> #include <cstdio> #include <cstring> #include <queue> using namespace std; #define N 1010 #define M 101000 const int INF = 1000000000; int n, m, sp, tp, cnte, cnte2, head[N], lowdis[N], head2[N], dep[N], tail[N]; bool vis[N]; class Edge { public: int u, v, w, next, next2; }; Edge edge1[M*2], edge2[M*2]; void addEdge1(int u, int v, int w) { edge1[cnte].u = u; edge1[cnte].v = v; edge1[cnte].w = w; edge1[cnte].next = head[u]; head[u] = cnte; edge1[cnte].next2 = tail[v]; tail[v] = cnte++; } void addEdge2(int u, int v, int w) { edge2[cnte2].u = u; edge2[cnte2].v = v; edge2[cnte2].w = w; edge2[cnte2].next = head2[u]; head2[u] = cnte2++; edge2[cnte2].v = u; edge2[cnte2].u = v; edge2[cnte2].w = 0; edge2[cnte2].next = head2[v]; head2[v] = cnte2++; } int spfa() { queue<int> q; for(int i = 1; i <= n; i++) { vis[i] = 0; lowdis[i] = INF; } vis[sp] = 1; lowdis[sp] = 0; q.push(sp); while(!q.empty()) { int cur = q.front(); q.pop(); vis[cur] = 0; for(int i = head[cur]; i != -1; i = edge1[i].next) { int v = edge1[i].v; if(lowdis[v] > lowdis[cur]+edge1[i].w) { lowdis[v] = lowdis[cur]+edge1[i].w; if(!vis[v]) { vis[v] = 1; q.push(v); } } } } return lowdis[tp] != INF; } void dfs(int cur) { for(int i = tail[cur]; i != -1; i = edge1[i].next2) { int u = edge1[i].u; if(lowdis[u]+edge1[i].w == lowdis[cur]) { addEdge2(u, cur, 1); if(!vis[u]) { vis[u] = 1; dfs(u); } } } } bool bfs() { memset(vis, 0, sizeof vis); memset(dep, -1, sizeof dep); queue<int> q; q.push(sp); vis[sp] = 1; dep[sp] = 1; while(!q.empty()) { int cur = q.front(); q.pop(); for(int i = head2[cur]; i != -1; i = edge2[i].next) { int v = edge2[i].v; if(!vis[v] && edge2[i].w > 0) { dep[v] = dep[cur]+1; vis[v] = 1; q.push(v); } } } return dep[tp] != -1; } int dfs2(int cur, int flow) { if(cur == tp) return flow; int res = 0; for(int i = head2[cur]; i != -1 && flow > res; i = edge2[i].next) { int v = edge2[i].v; if(edge2[i].w > 0 && dep[v] == dep[cur]+1) { int x = min(edge2[i].w, flow-res); int f = dfs2(v, x); edge2[i].w-=f; edge2[i^1].w+=f; res += f; } } if(!res) dep[cur] = -1; return res; } int dinic() { int res = 0; while(bfs()) { int t; while(t = dfs2(sp, INF)) { res += t; } } return res; } int main() { //freopen("C:\\Users\\Admin\\Desktop\\in.txt", "r", stdin); int t; scanf("%d", &t); while(t--) { cnte = 0; cnte2 = 0; memset(head, -1, sizeof head); memset(head2, -1, sizeof head2); memset(tail, -1, sizeof tail); int u, v, w; scanf("%d%d", &n, &m); for(int i = 0; i < m; i++) { scanf("%d%d%d", &u, &v, &w); addEdge1(u, v, w); } scanf("%d%d", &sp, &tp); int ans; if(!spfa()) ans = 0; else { dfs(tp); ans = dinic(); } printf("%d\n", ans); } return 0; }
标签:sub void bfs other pre string cas white time
原文地址:http://www.cnblogs.com/lytwajue/p/6814445.html