HDU-4975-a simple Gaussian elimination problem. (maximum Stream)

Question: Give the rows and columns of a Number Matrix with N rows and M columns, and the size of each element cannot exceed 9. Ask if such a matrix exists, whether the unique N (1 ≤ n ≤ 500), m (1 ≤ m ≤ 500 ).

Question link: http://acm.hdu.edu.cn/showproblem.php? PID = 1, 4975

--> Method such as: http://blog.csdn.net/scnu_jiechao/article/details/40658221

Do HDU-4888 first. When I do this again, I feel that this question is sb. After I submit the code, I will be sb. Why ??

The time for this question is relatively strict .. You can optimize the code of 4888 in the judgment ring, because the row-to-column edge in the original selected graph will be judged (n-1) During the judgment ring) * (m-1) + 1. If you create a new graph for the residual network, you will only be judged once when creating the graph!

Note: If the input fails, the Re is displayed. It is assumed that there are negative numbers in the input data ..

#include <cstdio>#include <cstring>#include <queue>#include <algorithm>using std::min;using std::queue;const int MAXN = 500 * 2 + 10;const int MAXM = 500 * 500 + 2 * MAXN;const int INF = 0x3f3f3f3f;struct EDGE{    int from;    int to;    int cap;    int flow;    int nxt;} edge[MAXM << 1];int N, M, kase;int sum;int S, T;int hed[MAXN], ecnt;int cur[MAXN], h[MAXN];bool impossible, bUnique;void Init(){    impossible = false;    bUnique = true;    ecnt = 0;    memset(hed, -1, sizeof(hed));}void AddEdge(int u, int v, int cap){    edge[ecnt].from = u;    edge[ecnt].to = v;    edge[ecnt].cap = cap;    edge[ecnt].flow = 0;    edge[ecnt].nxt = hed[u];    hed[u] = ecnt++;    edge[ecnt].from = v;    edge[ecnt].to = u;    edge[ecnt].cap = 0;    edge[ecnt].flow = 0;    edge[ecnt].nxt = hed[v];    hed[v] = ecnt++;}bool Bfs(){    memset(h, -1, sizeof(h));    queue<int> qu;    qu.push(S);    h[S] = 0;    while (!qu.empty())    {        int u = qu.front();        qu.pop();        for (int e = hed[u]; e != -1; e = edge[e].nxt)        {            int v = edge[e].to;            if (h[v] == -1 && edge[e].cap > edge[e].flow)            {                h[v] = h[u] + 1;                qu.push(v);            }        }    }    return h[T] != -1;}int Dfs(int u, int cap){    if (u == T || cap == 0) return cap;    int flow = 0, subFlow;    for (int e = cur[u]; e != -1; e = edge[e].nxt)    {        cur[u] = e;        int v = edge[e].to;        if (h[v] == h[u] + 1 && (subFlow = Dfs(v, min(cap, edge[e].cap - edge[e].flow))) > 0)        {            flow += subFlow;            edge[e].flow += subFlow;            edge[e ^ 1].flow -= subFlow;            cap -= subFlow;            if (cap == 0) break;        }    }    return flow;}int Dinic(){    int maxFlow = 0;    while (Bfs())    {        memcpy(cur, hed, sizeof(hed));        maxFlow += Dfs(S, INF);    }    return maxFlow;}int ReadInt(){    int ret = 0;    char ch;    while ((ch = getchar()) && ch >= '0' && ch <= '9')    {        ret = ret * 10 + ch - '0';    }    return ret;}void Read(){    int r, c;    int rsum = 0, csum = 0;    scanf("%d%d", &N, &M);    S = 0;    T = N + M + 1;    getchar();    for (int i = 1; i <= N; ++i)    {//        r = ReadInt();        scanf("%d", &r);        rsum += r;        AddEdge(S, i, r);    }    for (int i = 1; i <= M; ++i)    {//        c = ReadInt();        scanf("%d", &c);        csum += c;        AddEdge(i + N, T, c);    }    if (rsum != csum)    {        impossible = true;        return;    }    sum = rsum;    for (int i = 1; i <= N; ++i)    {        for (int j = M; j >= 1; --j)        {            AddEdge(i, j + N, 9);        }    }}void CheckPossible(){    if (impossible) return;    if (Dinic() != sum)    {        impossible = true;    }}void AddEdge(int u, int v){    edge[ecnt].to = v;    edge[ecnt].nxt = hed[u];    hed[u] = ecnt++;}void ReBuild(){    memset(hed, -1, sizeof(hed));    int total = ecnt;    ecnt = 0;    for (int e = 0; e < total; ++e)    {        if (edge[e].cap > edge[e].flow)        {            AddEdge(edge[e].from, edge[e].to);        }    }}bool vis[MAXN];bool CheckCircle(int x, int f){    vis[x] = true;    for (int e = hed[x]; e != -1; e = edge[e].nxt)    {        int v = edge[e].to;        if (v != f)        {            if (vis[v]) return true;            if (CheckCircle(v, x)) return true;        }    }    vis[x] = false;    return false;}void CheckUnique(){    if (impossible) return;    memset(vis, 0, sizeof(vis));    for (int i = 1; i <= N; ++i)    {        if (CheckCircle(i, -1))        {            bUnique = false;            return;        }    }}void Output(){    printf("Case #%d: ", ++kase);    if (impossible)    {        puts("So naive!");    }    else if (bUnique)    {        puts("So simple!");    }    else    {        puts("So young!");    }}int main(){    int T;    scanf("%d", &T);    while (T--)    {        Init();        Read();        CheckPossible();        ReBuild();        CheckUnique();        Output();    }    return 0;}

HDU-4975-a simple Gaussian elimination problem. (maximum Stream)