hdu1811Rank of Tetris

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链接：http://acm.hdu.edu.cn/showproblem.php?pid=1811

题意：中文题。

分析：先用并查集缩下点，然后用拓扑排序判断一些各种情况即可。

代码：

#include<map>#include<set>#include<cmath>#include<queue>#include<bitset>#include<math.h>#include<vector>#include<string>#include<stdio.h>#include<cstring>#include<iostream>#include<algorithm>#pragma comment(linker, "/STACK:102400000,102400000")using namespace std;const int N=10010;const int mod=100000000;const int MOD1=1000000007;const int MOD2=1000000009;const double EPS=0.00000001;typedef long long ll;const ll MOD=1000000007;const int INF=1000000010;const ll MAX=1ll<<55;const double pi=acos(-1.0);typedef double db;typedef unsigned long long ull;char s[5];int nn,f[N],x[N],y[N],z[N];int tot,d[N],u[N],v[N],pre[N];void add(int a,int b) {    v[tot]=b;pre[tot]=u[a];u[a]=tot++;}int find_f(int a) {    return f[a]==a ? a:f[a]=find_f(f[a]);}void unio(int a,int b) {    int fa=find_f(a),fb=find_f(b);    if (fa!=fb) f[fb]=fa,nn--;}int main(){    int a,b,i,k,n,m,l,r;    while (scanf("%d%d", &n, &m)!=EOF) {        for (i=0;i<n;i++) f[i]=i;        for (k=0,nn=n,i=1;i<=m;i++) {            scanf("%d%s%d", &a, s, &b);            if (s[0]=='<') { k++;x[k]=a;y[k]=b;z[k]=1; }            else if (s[0]=='>') { k++;x[k]=a;y[k]=b;z[k]=2; }                else unio(a,b);        }        memset(d,0,sizeof(d));        tot=0;memset(u,-1,sizeof(u));        for (i=0;i<n;i++) f[i]=find_f(i);        for (i=1;i<=k;i++)        if (z[i]==1) add(f[y[i]],f[x[i]]),d[f[x[i]]]++;        else add(f[x[i]],f[y[i]]),d[f[y[i]]]++;        k=0;l=1;r=0;        for (i=0;i<n;i++)        if (f[i]==i&&d[i]==0) y[++r]=i,x[r]=1;        for (;l<=r;l++)            for (i=u[y[l]];i!=-1;i=pre[i]) {                d[f[v[i]]]--;                if (d[f[v[i]]]==0) y[++r]=f[v[i]],x[r]=x[l]+1;            }        if (r<nn) printf("CONFLICT\n");        else {            for (k=1,i=1;i<r;i++)            if (x[i]==x[i+1]) { k=0;break ; }            if (!k) printf("UNCERTAIN\n");            else printf("OK\n");        }    }    return 0;}

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