poj 1273 Drainage Ditches

也是一道模板题目...敲一遍熟悉熟悉

#include <iostream>#include <algorithm>#include <cmath>#include <cstdio>#include <cstdlib>#include <cstring>#include <string>#include <vector>#include <set>#include <queue>#include <stack>#include <climits>//形如INT_MAX一类的#define MAX 205#define INF 0x7FFFFFFF# define eps 1e-5//#pragma comment(linker, "/STACK:36777216") ///传说中的外挂using namespace std;int cap[MAX][MAX],pre[MAX],flow[MAX];int m,n;int bfs(int s,int e){    queue<int >q;    memset(pre,-1,sizeof(pre));    pre[s] = 0;    flow[s] = INF;    q.push(s);    while(! q.empty())    {        int t = q.front();        q.pop();        if(t == e)            break;        for(int i=1; i<=m; i++)        {            if(pre[i] == -1 && cap[t][i] > 0 )            {                q.push(i);                pre[i] = t;                flow[i] = min(flow[t],cap[t][i]);            }        }    }    if(pre[e] == -1)        return -1;    return flow[e];}int maxflow(int s,int e){    int imp=0;    int sum=0;    while((imp = bfs(s,e)) != -1)    {        int ind = e;        while(ind != s)        {            cap[pre[ind]][ind] -= imp;            cap[ind][pre[ind]] += imp;            ind = pre[ind];        }        sum += imp;    }    return sum;}void init(){    memset(cap,0,sizeof(cap));    memset(flow,0,sizeof(flow));}int main(){    int a,b,c;    while(scanf("%d%d",&n,&m) != EOF)    {        init();        for(int i=0; i<n; i++)        {            scanf("%d%d%d",&a,&b,&c);            if(a == b)                continue;            cap[a][b] += c;        }        printf("%d\n",maxflow(1,m));    }    return 0;}