1.题面
http://poj.org/problem?id=1459
2.题意
水题
3.思路
看题意描述以为要拆点，但最后的求解出乎意料的简单
4.代码
/*****************************************************************
> File Name: cpp_acm.cpp
> Author: Uncle_Sugar
> Mail: [email protected]
> Created Time: Sat 01 Oct 2016 22:52:30 CST
*****************************************************************/
# include <cstdio>
# include <cstring>
# include <cctype>
# include <cmath>
# include <cstdlib>
# include <climits>
# include <iostream>
# include <iomanip>
# include <set>
# include <map>
# include <vector>
# include <stack>
# include <queue>
# include <algorithm>
using namespace std;
# define rep(i,a,b) for (i=a;i<=b;i++)
# define rrep(i,a,b) for (i=b;i>=a;i--)
struct QuickIO{
QuickIO(){const int SZ = 1<<20;
setvbuf(stdin ,new char[SZ],_IOFBF,SZ);
setvbuf(stdout,new char[SZ],_IOFBF,SZ);
} //*From programcaicai*//
}QIO;
template<class T>void PrintArray(T* first,T* last,char delim=' '){
for (;first!=last;first++) cout << *first << (first+1==last?'\n':delim);
}
/*
1.see the size of the input data before you select your algorithm
2.cin&cout is not recommended in ACM/ICPC
3.pay attention to the size you defined, for instance the size of edge is double the size of vertex
*/
const int debug = 1;
//# const int size = 10 + ;
const int INF = INT_MAX>>1;
typedef long long ll;
const int MAXN = 5000 + 10;
const int MAXM = MAXN*MAXN;
struct Edge{
int to, f, nxt;
}edge[MAXM];
int tot = 0;
int head[MAXN];
void init(){
tot = 0;
memset(head, -1, sizeof(head));
}
void addedge(int from, int to, int f){
edge[tot].to = to;edge[tot].f = f;
edge[tot].nxt = head[from]; head[from] = tot++;
edge[tot].to = from;edge[tot].f = 0;
edge[tot].nxt = head[to]; head[to] = tot++;
}
int level[MAXN];
bool bfs(int s, int t){
static queue<int> que;
while (!que.empty()) que.pop();
memset(level, 0, sizeof(level));
que.push(s); level[s] = 1;
while (!que.empty()){
int cur = que.front(); que.pop();
if (cur == t) return true;
for (int e = head[cur]; ~e; e = edge[e].nxt){
int to = edge[e].to, f = edge[e].f;
if (!level[to] && f){
level[to] = level[cur] + 1;
que.push(to);
}
}
}
return false;
}
int dfs(int u, int t, int sup){
if (u == t) return sup;
int ret = 0;
for (int e = head[u]; ~e; e = edge[e].nxt){
int cur = edge[e].to, f = edge[e].f;
if (level[cur] == level[u] + 1 && f){
int mi = min(sup - ret, f);
int tf = dfs(cur, t, mi);
edge[e].f -= tf; edge[e^1].f += tf;
ret += tf;
if (ret == sup) return ret;
}
}
return ret;
}
int Dinic(int s, int t){
int ret = 0;
while (bfs(s, t)) ret += dfs(s, t, INF);
return ret;
}
int main()
{
/*std::ios::sync_with_stdio(false);cin.tie(0);*/
int n, np, nc, m;
while (~scanf("%d%d%d%d", &n, &np, &nc, &m)){
init();
while (m--){
int a, b, c;
while (getchar() != '(');
scanf("%d,%d)%d", &a, &b, &c);
++a;++b;
addedge(a, b, c);
}
while (np--){
int a, b;
while (getchar() != '(');
scanf("%d)%d", &a, &b);
++a;
addedge(0, a, b);
}
while (nc--){
int a, b;
while (getchar() != '(');
scanf("%d)%d", &a, &b);
++a;
addedge(a, n+1, b);
}
ll ans = Dinic(0, n+1);
printf("%lld\n", ans);
}
return 0;
}
附上kuangbin的非递归dinic代码， 感谢kuangbin大神
地址是：点击打开链接
/*
最大流模板
dinic算法
*/
#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<iostream>
using namespace std;
const int INF=0x3f3f3f3f;
const int MAXN=150;//点数的最大值
const int MAXM=20500;//边数的最大值
struct Node
{
int from,to,next;
int cap;
}edge[MAXM];
int tol;
int dep[MAXN];//dep为点的层次
int head[MAXN];
int n;
void init()
{
tol=0;
memset(head,-1,sizeof(head));
}
void addedge(int u,int v,int w)//第一条变下标必须为偶数
{
edge[tol].from=u;
edge[tol].to=v;
edge[tol].cap=w;
edge[tol].next=head[u];
head[u]=tol++;
edge[tol].from=v;
edge[tol].to=u;
edge[tol].cap=0;
edge[tol].next=head[v];
head[v]=tol++;
}
int BFS(int start,int end)
{
int que[MAXN];
int front,rear;
front=rear=0;
memset(dep,-1,sizeof(dep));
que[rear++]=start;
dep[start]=0;
while(front!=rear)
{
int u=que[front++];
if(front==MAXN)front=0;
for(int i=head[u];i!=-1;i=edge[i].next)
{
int v=edge[i].to;
if(edge[i].cap>0&&dep[v]==-1)
{
dep[v]=dep[u]+1;
que[rear++]=v;
if(rear>=MAXN)rear=0;
if(v==end)return 1;
}
}
}
return 0;
}
int dinic(int start,int end)
{
int res=0;
int top;
int stack[MAXN];//stack为栈，存储当前增广路
int cur[MAXN];//存储当前点的后继
while(BFS(start,end))
{
memcpy(cur,head,sizeof(head));
int u=start;
top=0;
while(1)
{
if(u==end)
{
int min=INF;
int loc;
for(int i=0;i<top;i++)
if(min>edge[stack[i]].cap)
{
min=edge[stack[i]].cap;
loc=i;
}
for(int i=0;i<top;i++)
{
edge[stack[i]].cap-=min;
edge[stack[i]^1].cap+=min;
}
res+=min;
top=loc;
u=edge[stack[top]].from;
}
for(int i=cur[u];i!=-1;cur[u]=i=edge[i].next)
if(edge[i].cap!=0&&dep[u]+1==dep[edge[i].to])
break;
if(cur[u]!=-1)
{
stack[top++]=cur[u];
u=edge[cur[u]].to;
}
else
{
if(top==0)break;
dep[u]=-1;
u=edge[stack[--top]].from;
}
}
}
return res;
}
int main()//多源多汇点，在前面加个源点，后面加个汇点，转成单源单汇点
{
//freopen("in.txt","r",stdin);
//freopen("out.txt","w",stdout);
int start,end;
int np,nc,m;
int u,v,z;
while(scanf("%d%d%d%d",&n,&np,&nc,&m)!=EOF)
{
init();
while(m--)
{
while(getchar()!='(');
scanf("%d,%d)%d",&u,&v,&z);
u++;v++;
addedge(u,v,z);
}
while(np--)
{
while(getchar()!='(');
scanf("%d)%d",&u,&z);
u++;
addedge(0,u,z);
}
while(nc--)
{
while(getchar()!='(');
scanf("%d)%d",&u,&z);
u++;
addedge(u,n+1,z);
}
start=0;
end=n+1;
int ans=dinic(start,end);
printf("%d\n",ans);
}
return 0;
}