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