poj 1273 Drainage Ditches

来源：互联网发布：格式化后数据还能恢复吗编辑：程序博客网时间：2024/06/14 14:31
原题链接：http://poj.org/problem?id=1273
最大流模板题。。
#include<algorithm>#include<iostream>#include<cstdlib>#include<cstring>#include<cstdio>#include<vector>#include<map>using std::min;using std::find;using std::sort;using std::pair;using std::vector;using std::multimap;#define pb(e) push_back(e)#define sz(c) (int)(c).size()#define mp(a, b) make_pair(a, b)#define all(c) (c).begin(), (c).end()#define iter(c) __typeof((c).begin())#define cls(arr, val) memset(arr, val, sizeof(arr))#define cpresent(c, e) (find(all(c), (e)) != (c).end())#define rep(i, n) for(int i = 0; i < (int)n; i++)#define tr(c, i) for(iter(c) i = (c).begin(); i != (c).end(); ++i)const int N = 210;const int INF = 0x3f3f3f3f;struct Ford_Flukerson {    struct edge { int to, cap, next, rev; }G[N << 1];    bool vis[N];    int tot, head[N];    inline void init() {        tot = 0, cls(head, -1);    }    inline void add_edge(int u, int v, int cap) {        G[tot] = (edge){ v, cap, head[u], tot + 1 }; head[u] = tot++;        G[tot] = (edge){ u,   0, head[v], tot - 1 }; head[v] = tot++;    }    inline void built(int m) {        int u, v, f;        while(m--) {            scanf("%d %d %d", &u, &v, &f);            add_edge(u, v, f);        }    }    inline int dfs(int u, int t, int f) {        if(u == t) return f;        vis[u] = true;        for(int i = head[u]; ~i; i = G[i].next) {            edge &e = G[i];            if(!vis[e.to] && e.cap > 0) {                int d = dfs(e.to, t, min(e.cap, f));                if(d > 0 ) {                    e.cap -= d;                    G[e.rev].cap += d;                    return d;                }            }        }        return 0;    }    inline void max_flow(int n) {        int flow = 0;        while(true) {            cls(vis, false);            int f = dfs(1, n, INF);            if(!f) break;            flow += f;        }        printf("%d\n", flow);    }}go;int main() {#ifdef LOCAL    freopen("in.txt", "r", stdin);    freopen("out.txt", "w+", stdout);#endif    int n, m;    while(~scanf("%d %d", &m, &n)) {        go.init();        go.built(m);        go.max_flow(n);    }    return 0;}
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