Sgu 194 upstream and downstream network streams

Another template was created. This template should be OK, enough to cope with various network streams. Question: Give N points and m edges, there are two limits on the traffic of each edge. The limit cannot be greater than R or less than L. check whether there is a feasible solution.

#include<cstdio>#include<cstring>#include<iostream>#include<algorithm>using namespace std;const int maxn = 1000000;const int oo = 0x3777777;struct arc{    int to,cap,flow,next;    arc(int x = 0,int y=0,int z = 0,int u =0){        to = x;cap = y;        flow = z;next = u;    }};arc e[maxn];int head[maxn],d[maxn],tot,id[maxn],work[maxn];int S,T,q[maxn],hd,tail,n,m;void add(int u,int v,int cap,int flow,int ID){    id[tot] = ID;    e[tot] = arc(v,cap,flow,head[u]);    head[u] = tot++;    id[tot] = 0;    e[tot] = arc(u,0,-flow,head[v]);    head[v] = tot++;}bool bfs(){    for(int i=1;i<=T;i++)    d[i] = 0;    d[S] = 1;    hd = tail = 0;    q[tail++] = S;    while(hd != tail){        int u = q[hd++];        if(hd == maxn)hd  =0;        for(int i=head[u];i!=-1;i=e[i].next){             if(e[i].cap > e[i].flow && !d[e[i].to]){                d[e[i].to] = d[u] + 1;                q[tail++] = e[i].to;                if(tail == maxn)tail = 0;                if(T == e[i].to)return true;             }        }    }    return false;}int dfs(int u,int low){    int tmp = 0,f;    if(u==T||!low)return low;    for(int &i=work[u];i!=-1;i=e[i].next){            if(d[e[i].to] == d[u] + 1 && (f=dfs(e[i].to,min(low,e[i].cap - e[i].flow)))){               // tmp += f;                e[i].flow += f;                e[i^1].flow -= f;              //  low -= f;              //  if(!low)break;              return f;            }    }    return 0;}void init(){    memset(head,-1,sizeof(head));    tot = 0;}int du[maxn],dn[maxn],ans[maxn];int main(){    int u,v,down,up;    while(~scanf("%d%d",&n,&m)){        init();        for(int i=1;i<=m;i++){            scanf("%d%d%d%d",&u,&v,&down,&up);            add(u,v,up-down,0,i);            du[u] -= down;            du[v] += down;            dn[i] = down;        }        S = 0;T=n+1;        int Edge = tot;        for(int i=1;i<=n;i++){            if(du[i] > 0) add(S,i,du[i],0,0);            if(du[i] < 0) add(i,T,-du[i],0,0);        }        while(bfs())        {            for(int i=0; i<n+2; i++)            work[i]=head[i];            while(dfs(S,oo));        }        int flag = 0;        for(int i=head[S];i!=-1;i=e[i].next){            if(e[i].flow != e[i].cap){                flag = 1;break;            }        }        if(flag)puts("NO");        else {            puts("YES");            for(int i = 0;i<Edge;i++) ans[id[i]] = e[i].flow;            for(int i=1;i<=m;i++)                printf("%d\n",ans[i]+dn[i]);        }    }}

Sgu 194 upstream and downstream network streams