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: [email protected] > 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/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 = 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; }