UVALive 5903 Piece it together

来源：互联网发布：禅道数据库迁移linux 编辑：程序博客网时间：2024/05/08 09:09

一开始用的STL一直超时不能过，后来发现AC的代码基本都用的普通邻接表，然后改了一下13s，T=T，效率太低了。然后把某大神，详情戳链接http://acm.hust.edu.cn/vjudge/problem/viewSource.action?id=1199083的300+ms的代码加上自己的优化成功到了85ms，限时30s的程序还是挺有成就感的。

题目分析：

一个黑格子要和相邻的两个白格子构成一块，也就是成直角形状，因此，每个黑块必须和相邻上下白块中的一个匹配，同样左右白块必须也有一个和它匹配，将黑块拆成两个点，这样问题就变成二分图的匹配问题了。

我的TLE的代码：

#include <iostream>#include <sstream>#include <cstdio>#include <climits>#include <cstring>#include <cstdlib>#include <string>#include <stack>#include <map>#include <cmath>#include <vector>#include <queue>#include <algorithm>#define esp 1e-6#define pi acos(-1.0)#define pb push_back#define lson l, m, rt<<1#define rson m+1, r, rt<<1|1#define mp(a, b) make_pair((a), (b))#define in  freopen("in.txt", "r", stdin);#define out freopen("out.txt", "w", stdout);#define print(a) printf("%d\n",(a));#define bug puts("********))))))");#define stop  system("pause");#define Rep(i, c) for(__typeof(c.end()) i = c.begin(); i != c.end(); i++)#define inf 0x0f0f0f0fusing namespace std;typedef long long  LL;typedef vector<int> VI;typedef pair<int, int> pii;typedef vector<pii,int> VII;typedef vector<int>:: iterator IT;const int maxn = 555;char maze[maxn][maxn];int R, C;int flag[maxn * maxn];int match[maxn * maxn];VI g[maxn * maxn];vector<pii> BLK;bool dfs(int x){    for(int i = 0; i < g[x].size(); i++)    {        int v = g[x][i];        if(!flag[v])        {            flag[v] = 1;            if(match[v] == -1 || dfs(match[v]))            {                match[v] = x;                return true;            }        }    }    return false;}int main(void){    int T, t;    scanf("%d", &T);    memset(maze, -1, sizeof(maze));    for(t = 1;  t <= T; t++)    {        int b = 0, w = 0;        BLK.clear();        for(int i = 0; i < maxn*maxn; i++)            g[i].clear();        scanf("%d%d", &R, &C);        while(getchar() != '\n') ;        for(int i = 1; i <= R; i++)        {            scanf("%s", maze[i] + 1);            for(int j = 1;  j <= C; j++)                if(maze[i][j] == 'B')                    b++, BLK.pb(mp(i, j));                else if(maze[i][j] == 'W')                    w++;        }        if(b*2 != w)            puts("NO");        else        {            for(int i = 0; i < BLK.size(); i++)            {                int x = BLK[i].first;                int y = BLK[i].second;                if(maze[x-1][y] == 'W')                    g[i].pb((x-1)*C+y);                if(maze[x+1][y] == 'W')                    g[i].pb((x+1)*C+y);                if(maze[x][y-1] == 'W')                    g[i+b].pb(x*C+y-1);                if(maze[x][y+1] == 'W')                    g[i+b].pb(x*C+y+1);            }            memset(match, -1, sizeof(match));            int i;            for( i = 0; i < b; i++)            {                memset(flag, 0, sizeof(flag));                if(!dfs(i) || !dfs(i+b))                    break;            }            if(i < b)                puts("NO");            else puts("YES");        }    }    return 0;}

改后的代码：

#include <iostream>#include <sstream>#include <cstdio>#include <climits>#include <cstring>#include <cstdlib>#include <string>#include <stack>#include <map>#include <cmath>#include <vector>#include <queue>#include <algorithm>#define esp 1e-6#define pi acos(-1.0)#define pb push_back#define lson l, m, rt<<1#define rson m+1, r, rt<<1|1#define mp(a, b) make_pair((a), (b))#define in  freopen("in.txt", "r", stdin);#define out freopen("out.txt", "w", stdout);#define print(a) printf("%d\n",(a));#define bug puts("********))))))");#define stop  system("pause");#define Rep(i, c) for(__typeof(c.end()) i = c.begin(); i != c.end(); i++)#define inf 0x0f0f0f0fusing namespace std;typedef long long  LL;typedef vector<int> VI;typedef pair<int, int> pii;typedef vector<pii> VII;typedef vector<pii, int> VIII;typedef VI:: iterator IT;int n,m;char s[600][600];int B[600][600];int W[600][600];int link[300000];int vis[300000];int b,w;VII BLK;struct bian{    int v,next;}e[1000000];int head[300000];int num;int now;void add(int u,int v){    e[num].v=v;    e[num].next=head[u];    head[u]=num++;} bool dfs(int k){    for(int h=head[k];h!=-1;h=e[h].next)    {        int v=e[h].v;        if(vis[v]==now)            continue;        vis[v]=now;        if(link[v]==-1||dfs(link[v]))        {            link[v]=k;            return 1;        }    }    return 0;}int main(){    int T;    scanf("%d",&T);    while (T--)    {        BLK.clear();        num=0;        memset(head,-1,sizeof(head));        scanf("%d%d",&n,&m);        memset(s,0,sizeof(s));        for(int i=0;i<n;i++)            scanf("%s",s[i]);        b=w=0;        for(int i=0;i<n;i++)            for(int j=0;j<m;j++)            {                if(s[i][j]=='B')                    B[i][j]=++b, BLK.pb(mp(i, j));                if(s[i][j]=='W')                    W[i][j]=++w;            }        if(b*2!=w)        {            puts("NO");            continue;        }        else        {               for(int k = 0; k < BLK.size(); k++)               {                   int i = BLK[k].first;                   int j = BLK[k].second;                if(s[i][j]=='B')                {                    if(s[i-1][j]=='W')                        add(B[i][j],W[i-1][j]);                    if(s[i+1][j]=='W')                        add(B[i][j],W[i+1][j]);                    if(s[i][j-1]=='W')                        add(B[i][j]+b,W[i][j-1]);                    if(s[i][j+1]=='W')                        add(B[i][j]+b,W[i][j+1]);                }            }            memset(link,-1,sizeof(link)) ;            memset(vis,0,sizeof(vis));            int i;            for(i=1;i<=b*2;i++)            {                now=i;                if(!dfs(i))                    break;            }            if(i > b*2)                puts("YES");            else                puts("NO");        }    }    return 0;}

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