URAL 1277 Cops and Thieves 最小割
2017-11-27 16:11
363 查看
#include <bits/stdc++.h>
using namespace std;
const int maxn = 210;
const int maxm = 100010;
const int inf = 0x3f3f3f3f;
struct G
{
int v, cap, next;
G() {}
G(int v, int cap, int next) : v(v), cap(cap), next(next) {}
} E[maxm];
int p[maxn], T;
int d[maxn], temp_p[maxn], qw[maxn]; //d顶点到源点的距离标号,temp_p当前狐优化,qw队列
void init()
{
memset(p, -1, sizeof(p));
T = 0;
}
void add(int u, int v, int cap)
{
E[T] = G(v, cap, p[u]);
p[u] = T++;
E[T] = G(u, 0, p[v]);
p[v] = T++;
}
bool bfs(int st, int en, int n)
{
int i, u, v, head, tail;
for(i = 0; i <= n; i++) d[i] = -1;
head = tail = 0;
d[st] = 0;
qw[tail] = st;
while(head <= tail)
{
u = qw[head++];
for(i = p[u]; i + 1; i = E[i].next)
{
v = E[i].v;
if(d[v] == -1 && E[i].cap > 0)
{
d[v] = d[u] + 1;
qw[++tail] = v;
}
}
}
return (d[en] != -1);
}
int dfs(int u, int en, int f)
{
if(u == en || f == 0) return f;
int flow = 0, temp;
for(; temp_p[u] + 1; temp_p[u] = E[temp_p[u]].next)
{
G& e = E[temp_p[u]];
if(d[u] + 1 == d[e.v])
{
temp = dfs(e.v, en, min(f, e.cap));
if(temp > 0)
{
e.cap -= temp;
E[temp_p[u] ^ 1].cap += temp;
flow += temp;
f -= temp;
if(f == 0) break;
}
}
}
return flow;
}
int dinic(int st, int en, int n)
{
int i, ans = 0;
while(bfs(st, en, n))
{
for(i = 0; i <= n; i++) temp_p[i] = p[i];
ans += dfs(st, en, inf);
}
return ans;
}
int main(){
int k, n, m, s, f;
while(~scanf("%d", &k)){
init();
scanf("%d %d %d %d", &n,&m,&s,&f);
for(int i=1; i<=n; i++){
int x;
scanf("%d", &x);
add(i, n+i, x);
}
for(int i=1; i<=m; i++){
int a,b;
scanf("%d %d", &a,&b);
add(a+n, b, inf);
add(b+n, a, inf);
}
int ans = dinic(f+n, s, 2*n+1);
if(ans <= k && s != f) puts("YES");
else puts("NO");
}
}
相关文章推荐
- URAL 1277 Cops and Thieves 最小割 无向图点带权点连通度
- Ural 1277 - Cops and Thieves 无向图的最小点割
- ural 1277. Cops and Thieves【最小割】
- ural 1277. Cops and Thieves【最小割】
- Ural 1277 Cops and Thieves(最小点割集/最小割)
- 【Ural1277】 Cops and Thieves 无向图点连通度问题
- URAL 1277 Cops and Thieves
- URAL 1277 Cops and Thieves
- UVAL1277_Cops and Thieves
- 1277. Cops and Thieves
- uva 1277 Cops and Thieves(完成阻击所需要的最少人数)
- Ural 1277 cops ans thieves (最小割模型)
- URAL 1277 网络流最小割 解题报告
- 【线性筛】【筛法求素数】【素数判定】URAL - 2102 - Michael and Cryptography
- ural 1982. Electrification Plan (最小生成树)
- [CodeForces 677D] Vanya and Treasure (二维树状数组+静态前缀最小值)
- LightOJ -1029--Civil and Evil Engineer(最小生成树&&最大生成树)
- URAL 1430 Crime and Punishment
- URAL(timus) 1272 Non-Yekaterinburg Subway(最小生成树)
- HDU3870-Caught these thieves(最小割->偶图->最短路问题)