SGU 194 无源汇的上下界可行流

很裸的模板题，直接搞起

#include <iostream>#include <algorithm>#include <cstring>#include <string>#include <cstdio>#include <cmath>#include <queue>#include <map>#include <set>#define MAXN 555#define MAXM 555555#define INF 1000000007using namespace std;struct node{    int ver;    // vertex    int cap;    // capacity    int flow;   // current flow in this arc    int next, rev;}edge[MAXM];int dist[MAXN], numbs[MAXN], src, des, n;int head[MAXN], e;void add(int x, int y, int c){       //e记录边的总数    edge[e].ver = y;    edge[e].cap = c;    edge[e].flow = 0;    edge[e].rev = e + 1;        //反向边在edge中的下标位置    edge[e].next = head[x];   //记录以x为起点的上一条边在edge中的下标位置    head[x] = e++;           //以x为起点的边的位置    //反向边    edge[e].ver = x;    edge[e].cap = 0;  //反向边的初始容量为0    edge[e].flow = 0;    edge[e].rev = e - 1;    edge[e].next = head[y];    head[y] = e++;}void rev_BFS(){    int Q[MAXN], qhead = 0, qtail = 0;    for(int i = 1; i <= n; ++i)    {        dist[i] = MAXN;        numbs[i] = 0;    }    Q[qtail++] = des;    dist[des] = 0;    numbs[0] = 1;    while(qhead != qtail)    {        int v = Q[qhead++];        for(int i = head[v]; i != -1; i = edge[i].next)        {            if(edge[edge[i].rev].cap == 0 || dist[edge[i].ver] < MAXN)continue;            dist[edge[i].ver] = dist[v] + 1;            ++numbs[dist[edge[i].ver]];            Q[qtail++] = edge[i].ver;        }    }}void init(){    e = 0;    memset(head, -1, sizeof(head));}int maxflow(){    int u, totalflow = 0;    int Curhead[MAXN], revpath[MAXN];    for(int i = 1; i <= n; ++i)Curhead[i] = head[i];    u = src;    while(dist[src] < n)    {        if(u == des)     // find an augmenting path        {            int augflow = INF;            for(int i = src; i != des; i = edge[Curhead[i]].ver)                augflow = min(augflow, edge[Curhead[i]].cap);            for(int i = src; i != des; i = edge[Curhead[i]].ver)            {                edge[Curhead[i]].cap -= augflow;                edge[edge[Curhead[i]].rev].cap += augflow;                edge[Curhead[i]].flow += augflow;                edge[edge[Curhead[i]].rev].flow -= augflow;            }            totalflow += augflow;            u = src;        }        int i;        for(i = Curhead[u]; i != -1; i = edge[i].next)            if(edge[i].cap > 0 && dist[u] == dist[edge[i].ver] + 1)break;        if(i != -1)     // find an admissible arc, then Advance        {            Curhead[u] = i;            revpath[edge[i].ver] = edge[i].rev;            u = edge[i].ver;        }        else        // no admissible arc, then relabel this vertex        {            if(0 == (--numbs[dist[u]]))break;    // GAP cut, Important!            Curhead[u] = head[u];            int mindist = n;            for(int j = head[u]; j != -1; j = edge[j].next)                if(edge[j].cap > 0)mindist = min(mindist, dist[edge[j].ver]);            dist[u] = mindist + 1;            ++numbs[dist[u]];            if(u != src)                u = edge[revpath[u]].ver;    // Backtrack        }    }    return totalflow;}int xj[MAXN];int nt, m;int low[MAXM];void solve(){    for(int i = head[src]; i != -1; i = edge[i].next)        if(edge[i].cap > 0)        {            printf("NO\n");            return;        }    printf("YES\n");    for(int i = 0; i < m; i++)        printf("%d\n", edge[i * 2].flow + low[i + 1]);}int main(){    int u, v, up;    while(scanf("%d%d", &nt, &m) != EOF)    {        init();        memset(xj, 0, sizeof(xj));        for(int i = 1; i <= m; i++)        {            scanf("%d%d%d%d", &u, &v, &low[i], &up);            add(u, v, up - low[i]);            xj[v] += low[i];            xj[u] -= low[i];        }        src = nt + 1;        des = nt + 2;        n = des;        for(int i = 1; i <= nt; i++)            if(xj[i] > 0) add(src, i, xj[i]);            else if(xj[i] < 0) add(i, des, -xj[i]);        rev_BFS();        maxflow();        solve();    }    return 0;}