HihoCoder #1369 : 网络流一·Ford-Fulkerson算法

1.题面

http://hihocoder.com/problemset/problem/1369

2.题意

给你一张图，求从１到n的最大流

3.思路

使用Dinic算法

4.代码

/*****************************************************************    > File Name: cpp_acm.cpp    > Author: Uncle_Sugar    > Mail: [e-mail]    > Created Time: Sun 02 Oct 2016 13:36:50 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--)# define mset(aim, val) memset((aim), (val), sizeof(aim))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/ICPC3.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 = 100 + 100000;const int MAXM = 100 + 200000;struct Edge{int to, nxt, f;};struct Dinic_MaxFlow{int head[MAXN], tot;Edge edge[MAXM];int level[MAXN];void init(){tot = 0; mset(head, -1);}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++;}bool bfs(int s, int t){static queue<int> que;while (!que.empty()) que.pop();mset(level, 0);level[s] = 1;que.push(s);while (!que.empty()){int c = que.front();que.pop();if (c == t) return true;for (int e = head[c]; ~e; e = edge[e].nxt){int to = edge[e].to, f = edge[e].f;//# cout << "to = " << to << endl;if (!level[to] && f){level[to] = level[c] + 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 to = edge[e].to, f = edge[e].f;//# cout << "to = " << to << endl;if (level[to] == level[u] + 1 && f){int mi = min(sup - ret, f);int tf = dfs(to, 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;}}dinic;int main(){/*std::ios::sync_with_stdio(false);cin.tie(0);*/int n, m;while (~scanf("%d%d", &n, &m)){dinic.init();for (int i = 0; i < m; i++){int a, b, c;scanf("%d%d%d", &a, &b, &c);dinic.addedge(a, b, c);//# dinic.addedge(b, a, c);}printf("%d\n", dinic.Dinic(1, n));//# cout << dinic.Dinic(1, n) << endl;}return 0;}