hdu 1532 Drainage Ditches 最大流 水题

//0MS268K#include <cstdio>#include <iostream>#include <cstring>#include <queue>#include <vector>#include <algorithm>using namespace std;struct edge{    int to, cap, rev;    edge(int to, int cap, int rev) :        to(to), cap(cap), rev(rev) {}};const int inf = 0x7fffffff;const int maxv = 200;const int maxe = 200;vector<edge> G[maxv+5];int level[maxv+5];int iter[maxv+5];inline void AddEdge(int from, int to, int cap){    G[from].push_back(edge(to, cap, G[to].size()));    G[to].push_back(edge(from, 0, G[from].size() - 1));}void bfs(int s){    memset(level, -1, sizeof(level));    queue<int> que;    level[s] = 0;    que.push(s);    while(!que.empty()){        int v = que.front(); que.pop();        for(int i=0; i<G[v].size(); i++){            edge& e = G[v][i];            if(e.cap > 0 && level[e.to] < 0){                level[e.to] = level[v] + 1;                que.push(e.to);            }        }    }}int dfs(int v, int t, int f){    if(v == t) return f;    for(int& i=iter[v]; i<G[v].size(); i++){        edge& e = G[v][i];        if(e.cap > 0 && level[v] < level[e.to]){            int d = dfs(e.to, t, min(f, e.cap));            if(d > 0){                e.cap -= d;                G[e.to][e.rev].cap += d;                return d;            }        }    }    return 0;}int MaxFlow(int s, int t){    int flow = 0;    while(1){        bfs(s);        if(level[t] < 0) return flow;        memset(iter, 0, sizeof(iter));        int f;        while((f = dfs(s, t, inf)) > 0){            flow += f;        }    }}int main(){    int N, M;    while(~scanf("%d%d", &N, &M)){ //N是边数，M是顶点数        for(int i=1; i<=N; i++)            G[i].clear();        int X, Y, C;        for(int i=1; i<=N; i++){            scanf("%d%d%d", &X, &Y, &C);            AddEdge(X, Y, C);        }        printf("%d\n", MaxFlow(1, M));    }    return 0;}

另一种数据结构

//15MS280K#include <cstdio>#include <iostream>#include <cstring>#include <queue>#include <vector>#include <algorithm>using namespace std;struct edge{    int to, cap, flow;    edge(int to, int cap, int flow) :        to(to), cap(cap), flow(flow) {}};const int inf = 0x7fffffff;const int maxv = 200;const int maxe = 200;vector<int> G[maxv+5];vector<edge> es;int level[maxv+5];int iter[maxv+5];inline void AddEdge(int from, int to, int cap){    es.push_back(edge(to, cap, 0));    G[from].push_back(es.size() - 1);    es.push_back(edge(from, 0, 0));    G[to].push_back(es.size() - 1);}void bfs(int s){    memset(level, -1, sizeof(level));    queue<int> que;    level[s] = 0;    que.push(s);    while(!que.empty()){        int v = que.front(); que.pop();        for(int i=0; i<G[v].size(); i++){            edge& e = es[G[v][i]];            if(e.flow < e.cap && level[e.to] < 0){                level[e.to] = level[v] + 1;                que.push(e.to);            }        }    }}int dfs(int v, int t, int rem){    if(v == t) return rem;    for(int& i=iter[v]; i<G[v].size(); i++){        edge& e = es[G[v][i]];        if(e.flow < e.cap && level[v] < level[e.to]){            int d = dfs(e.to, t, min(rem, e.cap - e.flow));            if(d > 0){                e.flow += d;                es[G[v][i]^1].flow -= d;                return d;            }        }    }    return 0;}int MaxFlow(int s, int t){    int flow = 0;    while(true){        bfs(s);        if(level[t] < 0) return flow;        memset(iter, 0, sizeof(iter));        int f;        while((f = dfs(s, t, inf)) > 0){            flow += f;        }    }}int main(){    int N, M;    while(~scanf("%d%d", &N, &M)){ //N是边数，M是顶点数        for(int i=1; i<=N; i++)            G[i].clear();        es.clear();        int X, Y, C;        for(int i=1; i<=N; i++){            scanf("%d%d%d", &X, &Y, &C);            AddEdge(X, Y, C);        }        printf("%d\n", MaxFlow(1, M));    }    return 0;}