poj 2375

来源：互联网发布：国内的人工智能龙头股编辑：程序博客网时间：2024/06/05 07:39
#include <iostream>#include <cstring>#include <cstdio>#include <algorithm>#include <cmath>#define N 510using namespace std;struct Node{    int v,next;}e[N*N*4];int head[N*N],e_num,num,od[N*N],id[N*N];int map[N][N],temp_map[N][N];int dir[][2]={0,1,1,0};bool vis[N*N];int low[N*N],stack[N*N],s[N*N],scc_num,top,s_n,p[N*N];void add_edge( int u, int v){    e[e_num].v=v;    e[e_num].next=head[u];    head[u]=e_num++;}void get_map(int m, int n ){    memset(head,-1,sizeof(head));    e_num=0;    for( int i=1; i<=m; i++ )    {        for( int j=1; j<=n; j++ )        {            for( int k=0; k<2; k++ )            {                int x=i+dir[k][0];                int y=j+dir[k][1];                if(x>=1&&x<=m&&y>=1&&y<=n)                {                    if(map[x][y]<=map[i][j])                        add_edge(temp_map[i][j],temp_map[x][y]);                    if(map[x][y]>=map[i][j])                        add_edge(temp_map[x][y],temp_map[i][j]);                }            }        }    }}void dfs( int u, int dfs_num, int &scc_num){    low[u]=++dfs_num;    s[++s_n]=u;    stack[++top]=u;    for( int i=head[u]; i!=-1; i=e[i].next )    {        if(!low[e[i].v])            dfs(e[i].v,dfs_num,scc_num);            else if(p[e[i].v]==0)            {                while(low[stack[top]]>low[e[i].v])--top;            }    }    if( stack[top]==u )    {        top--;        scc_num++;        do        {            p[s[s_n]]=scc_num;        }while(s[s_n--]!=u);    }    return ;}void work(){    int scc_num=0,dfs_num=0;    memset(p,0,sizeof(p));    memset(low,0,sizeof(low));    s_n=top=0;    for( int i=1; i<=num; i++ )    {        if(!low[i])dfs(i,dfs_num,scc_num);    }    memset(od,0,sizeof(od));    memset(id,0,sizeof(id));    for( int u=1;u<=num; u++ )    {        for( int i=head[u];i!=-1;i=e[i].next)        {            int v=e[i].v;            if(p[u]!=p[v])od[p[u]]++,id[p[v]]++;        }    }    int i_num=0,o_num=0;    for( int i=1; i<=scc_num; i++)    {        if(!od[i])o_num++;        if(!id[i])i_num++;    }    if(scc_num==1)printf("0\n");    else printf("%d\n",max(i_num,o_num));}int main(){   // freopen("in.txt","r",stdin);    int W,L;    while( ~scanf("%d%d",&W,&L))    {        num=0;        for( int i=1;i<=L; i++ )        for( int j=1;j<=W; j++ )        {            scanf("%d",&map[i][j]);            temp_map[i][j]=++num;        }        get_map(L,W);        work();    }    return 0;}