Dinic's algorithm

#include <bits/stdc++.h>
using namespace std;

const int N=1000;
const int M=500;
const int inf=1e9;

struct Edge
{
    int u, v, cap, flow, next;
} grana[M];

int n, m, head[N], dist[N];
int E, src, snk;

void add_edge (int u, int v, int c1, int c2)
{
    grana[E++]=(Edge){u, v, c1, 0, head[u]};
    head[u]=E-1;
    grana[E++]=(Edge){v, u, c2, 0, head[v]};
    head[v]=E-1;
}

bool bfs ()
{
    fill(dist, dist+N, -1);
    queue<int> q;
    dist[src]=0;

    for (q.push(src);!q.empty();q.pop())
    {
        int v=q.front();
        for (int e=head[v];e!=-1;e=grana[e].next)
        {
            int xt=grana[e].v;
            if (grana[e].cap>grana[e].flow && dist[xt]==-1)
            {
                dist[xt]=dist[v]+1;
                q.push(xt);
            }
        }
    }

    return (dist[snk]!=-1);
}

int dfs (int v, int minCap)
{
    if (minCap==0) return 0;
    if (v==snk) return minCap;

    for (int e=head[v];e!=-1;e=grana[e].next)
    {
        int xt=grana[e].v;
        if (dist[xt]!=dist[v]+1) continue;
        int augment=dfs(xt, min(minCap, grana[e].cap-grana[e].flow));
        if (augment)
        {
            grana[e].flow+=augment;
            grana[e^1].flow-=augment;
            return augment;
        }
    }

    return 0;
}

int Dinic()
{
    int flow=0;
    src=1, snk=n;

    while (true)
    {
        if (!bfs()) break;
        while (true)
        {
            int curFlow=dfs(src, inf);
            if (curFlow==0) break;
            flow+=curFlow;
        }
    }

    return flow;
}

int main()
{
    scanf ("%d%d", &n, &m);
    fill(head, head+N, -1);
    for (int i=0;i<m;i++)
    {
        int a, b, c;
        scanf ("%d%d%d", &a, &b, &c);
        add_edge(a, b, c, 0);
    }

    printf ("%d", Dinic());

    return 0;
}