网络流，最基础的增广路算法！

来源：互联网发布：ubuntu 13.04安装失败编辑：程序博客网时间：2024/05/29 20:00
哈哈，我的第一个网络流！
#include<iostream>#include<cstdio>#include<algorithm>#include<cstring>using namespace std;const int MAXN = 1005;const int INF = 0x7ffffff;struct edge_{    int c, f;}edge[MAXN][MAXN];int n, m;int flag[MAXN], pre[MAXN], alpha[MAXN], que[MAXN];int h, t, v, u;int ford(){    while(1){        memset(flag, -1, sizeof(flag));        memset(pre, -1, sizeof(pre));        memset(alpha, -1, sizeof(alpha));        flag[0] = 0, pre[0] = 0, alpha[0] = INF;        t = 0, h = 1;        que[t] = 0;        while(t < h && flag[n - 1] ==  -1){            u = que[t], t++;            for(v = 0; v < n; v ++){                if(flag[v] == -1){                    if(edge[u][v].c < INF && edge[u][v].f < edge[u][v].c){                        flag[v] = 0, pre[v] = u;                        alpha[v] = min(alpha[u], edge[u][v].c - edge[u][v].f);                        que[h] = v, h++;                    }                    else if(edge[v][u].c < INF && edge[v][u].f > 0){                        flag[v] = 0, pre[v] = -u;                        alpha[v] = min(alpha[u], edge[v][u].f);                        que[h] = v, h++;                    }                }            }            flag[u] = 1;        }        if(flag[n - 1] == -1 || alpha[n - 1] == 0)            break;        v = n - 1, u = abs(pre[v]);        int a = alpha[v];        while(1){            if(edge[u][v].f < INF)                edge[u][v].f += a;            else                edge[v][u].f -= a;            if(v == 0)                break;            v = u, u = abs(pre[v]);        }    }    int maxFord = 0;    for(int i = 0; i < n; i++)        for(int j = 0; j < n; j++){            if(i == 0 && edge[i][j].f < INF)                maxFord += edge[i][j].f;            if(edge[i][j].f < INF)                printf("%d -> %d : %d\n", i, j, edge[i][j].f);    }    return maxFord;}int main(){    freopen("in.in", "r", stdin);    int u, v, c, f;    cin>> n >> m;    for(int i = 0; i < n; i++)        for(int j = 0; j < n; j++)            edge[i][j].c = edge[i][j].f = INF;    for(int i = 0; i < m; i++){        cin>> u >> v >> c >> f;        edge[u][v].c = c;        edge[u][v].f = f;    }    cout<< ford() <<endl;    return 0;}