HDU 4975 (hangdian multi-school #10 1005) A simple Gaussian elimination problem. (the largest stream in the network flow)

Address: HDU 4975

This question is speechless... I thought it would take a more advanced method to solve this problem, but the result is still the old method. Is it really good to get stuck in this way .... During the competition, we used the method of judging the ring. We kept fighting .. Later, I changed the matrix DP Method and added the pruning method .. Speechless ..

The Code is as follows:

#include <cstdio>#include <cstring>#include <algorithm>#include <iostream>#include <cstdio>#include <string>#include <cstring>#include <stdlib.h>#include <math.h>#include <ctype.h>#include <queue>#include <map>#include <set>#include <algorithm>using namespace std;const int INF=0x3f3f3f3f;int head[1010], source, sink, nv, cnt, vis[610][600], mp[600][600];int cur[1010], num[1010], d[1010], pre[1010];int a[600], b[600];struct node{    int u, v, cap, next;} edge[1000000];void add(int u, int v, int cap){    edge[cnt].v=v;    edge[cnt].cap=cap;    edge[cnt].next=head[u];    head[u]=cnt++;    edge[cnt].v=u;    edge[cnt].cap=0;    edge[cnt].next=head[v];    head[v]=cnt++;}void bfs(){    memset(num,0,sizeof(num));    memset(d,-1,sizeof(d));    queue<int>q;    q.push(sink);    d[sink]=0;    num[0]=1;    while(!q.empty())    {        int u=q.front();        q.pop();        for(int i=head[u]; i!=-1; i=edge[i].next)        {            int v=edge[i].v;            if(d[v]==-1)            {                d[v]=d[u]+1;                num[d[v]]++;                q.push(v);            }        }    }}int isap(){    memcpy(cur,head,sizeof(cur));    int flow=0, u=pre[source]=source, i;    bfs();    while(d[source]<nv)    {        if(u==sink)        {            int f=INF, pos;            for(i=source; i!=sink; i=edge[cur[i]].v)            {                if(f>edge[cur[i]].cap)                {                    f=edge[cur[i]].cap;                    pos=i;                }            }            for(i=source; i!=sink; i=edge[cur[i]].v)            {                edge[cur[i]].cap-=f;                edge[cur[i]^1].cap+=f;            }            flow+=f;            u=pos;        }        for(i=cur[u]; i!=-1; i=edge[i].next)        {            if(d[edge[i].v]+1==d[u]&&edge[i].cap)                break;        }        if(i!=-1)        {            cur[u]=i;            pre[edge[i].v]=u;            u=edge[i].v;        }        else        {            if(--num[d[u]]==0) break;            int mind=nv;            for(i=head[u]; i!=-1; i=edge[i].next)            {                if(mind>d[edge[i].v]&&edge[i].cap)                {                    mind=d[edge[i].v];                    cur[u]=i;                }            }            d[u]=mind+1;            num[d[u]]++;            u=pre[u];        }    }    return flow;}bool panduan(int n,int m){    memset(vis,0,sizeof(vis));    int i, j, k;    for(i=1;i<=n;i++)    {        if(a[i]==0||a[i]==9*m) continue ;        for(j=1;j<=m;j++)        {            if(b[j]==0||b[j]==9*n) continue ;            for(k=j+1;k<=m;k++)            {                int t1=0, t2=0;                if(mp[i][j]&&mp[i][k]!=9)                {                    if(vis[j][k]) return 1;                    t1=1;                }                if(mp[i][k]&&mp[i][j]!=9)                {                    if(vis[k][j]) return 1;                    t2=1;                }                if(t1) vis[k][j]=1;                if(t2) vis[j][k]=1;            }        }    }    return 0;}int read(){    int x = 0;    char ch = ' ';    while(ch < '0' || ch > '9') ch = getchar();    while(ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();    return x;}int main(){    int t, i, j, n, m, sum1, sum2, num=0;    t=read();    while(t--)    {        num++;        n=read();        m=read();        sum1=sum2=0;        memset(head,-1,sizeof(head));        cnt=0;        source=0;        sink=n+m+1;        nv=sink+1;        for(i=1; i<=n; i++)        {            a[i]=read();            sum1+=a[i];        }        for(i=1; i<=m; i++)        {            b[i]=read();            sum2+=b[i];        }        printf("Case #%d: ",num);        if(sum1!=sum2)        {            puts("So naive!");            continue ;        }        for(i=1; i<=n; i++)        {            add(source,i,a[i]);            for(j=1; j<=m; j++)            {                add(i,j+n,9);            }        }        for(i=1; i<=m; i++)        {            add(i+n,sink,b[i]);        }        int ans=isap();        if(ans!=sum1)        {            puts("So naive!");            continue ;        }        for(i=1;i<=n;i++)        {            for(j=head[i];j!=-1;j=edge[j].next)            {                int v=edge[j].v;                if(v>n&&v<=n+m)                    mp[i][v-n]=9-edge[j].cap;            }        }        if(panduan(n,m))        {            puts("So young!");        }        else            puts("So simple!");    }    return 0;}