delete pics to save space

p.CH1813.cpp

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+//http://contest-hunter.org:83/contest/0x18%E3%80%8C%E5%9F%BA%E6%9C%AC%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E3%80%8D%E7%BB%83%E4%B9%A0/1813%20%E5%8F%8C%E6%A0%88%E6%8E%92%E5%BA%8F
+#include<cstdio>
+#include<cstring>
+#include<algorithm>
+using namespace std;
+const int maxn=1005;
+int T,n,a[maxn],co[maxn],s1[maxn],c1,s2[maxn],c2;
+struct JUDGE
+{
+	int k[maxn];
+	struct Edge { int v; Edge *nxt; };
+	Edge mem[maxn*maxn*2],*G[maxn],*ecnt;
+	inline void init()
+	{
+		memset(G,0,sizeof(G)); ecnt=mem;
+		memset(co,0,sizeof(co));
+	}
+	inline void AddEdge(int u,int v) { ecnt->v=v; ecnt->nxt=G[u]; G[u]=ecnt++; }
+	bool dfs(int u,int c)
+	{
+		if(co[u]) return co[u]==c;
+		co[u]=c;
+		for(Edge *it=G[u];it;it=it->nxt) if(!dfs(it->v,3-c)) return false;
+		return true;
+	}
+	bool ok()
+	{
+		k[n+1]=n+1;
+		for(int i=n;i>=1;i--) k[i]=min(k[i+1],a[i]);
+		for(int i=1;i<=n;i++) for(int j=i+1;j<=n;j++)
+			if(k[j+1]<a[i]&&a[i]<a[j])
+			{
+				AddEdge(i,j);
+				AddEdge(j,i);
+			}
+		for(int i=1;i<=n;i++) if(!co[i]&&!dfs(i,1)) return false;
+		return true;
+	}
+}jg;
+inline void solve()
+{
+	scanf("%d",&n);
+	for(int i=1;i<=n;i++) scanf("%d",&a[i]);
+	jg.init();
+	if(!jg.ok()) { puts("0"); return; }
+	int now=1; c1=c2=0;
+	for(int i=1;i<=n;i++)
+	{
+		if(co[i]==1) { s1[c1++]=a[i]; printf("a "); }
+		else { s2[c2++]=a[i]; printf("c "); }
+		while(true)
+		{
+			if(c1&&s1[c1-1]==now) { printf("b "); c1--; now++; }
+			else if(c2&&s2[c2-1]==now) { printf("d "); c2--; now++; }
+			else break;
+		}
+	}
+	puts("");
+}
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	scanf("%d",&T);
+	while(T-->0) solve();
+	return 0;
+}