delete pics to save space

2.1618.cpp

@@ -0,0 +1,75 @@
+#include<iostream>
+#include<algorithm>
+using namespace std;
+
+const int maxn=5005;
+int a[maxn],l[maxn][maxn],r[maxn][maxn];
+// l[i][j]±íʾϱêСÓÚjÇÒÖµ±ÈNi´óµÄÊýÖÐ×îСֵµÄλÖÃ
+// r[i][j]±íʾϱê´óÓÚjÇÒÖµ±ÈNiСµÄÊýÖÐ×î´óÖµµÄλÖÃ
+int k;
+
+bool solve()
+{
+    for(int i=1;i<=k;i++)
+	{
+	    l[i][0]=0;
+	    for(int j=1;j<i;j++)
+		{ // ö¾ÙNq,ÕÒNp
+		    if(a[i]>=a[j])
+			    l[i][j]=l[i][j-1];
+		    else if(!l[i][j-1]||a[j]<a[l[i][j-1]])
+			    l[i][j]=j;
+		    else
+			    l[i][j]=l[i][j-1];
+		}
+	}
+    for(int i=1;i<=k;i++)
+	{
+	    r[i][k+1]=0;
+	    for(int j=k;j>i;j--)
+		{// ö¾ÙNr,ÕÒNs
+		    if(a[i]<=a[j])
+			    r[i][j]=r[i][j+1];
+		    else if(!r[i][j+1]||a[j]>a[r[i][j+1]])
+			    r[i][j]=j;
+		    else 
+			    r[i][j]=r[i][j+1];
+		}
+	}
+	//ö¾Ùr£¬q£¬ÕÒp£¬s¾Í±ä³ÉÁ˳£Êýʱ¼ä¡£¸´ÔÓ¶ÈÓÉn^4±ä³ÉÁËn^2.
+    for(int i=1;i<=k;i++)
+	{
+	    for(int j=i+1;j<=k;j++)
+		{
+		    if(!l[j][i-1]||!r[i][j+1]||a[i]<=a[j])
+			    continue;
+		    int p=l[j][i-1],s=r[i][j+1];
+		    if(a[j]<a[p]&&a[p]<a[s]&&a[s]<a[i])
+			    return true;
+		}
+	}		
+    return false;
+}
+
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif 
+    ios::sync_with_stdio(false);
+    int T;
+    cin>>T;
+    while(T--)
+	{
+	    cin>>k;
+	    for(int i=1;i<=k;i++) cin>>a[i];
+	    if(solve()) cout<<"YES\n";
+	    else
+		{
+		    reverse(a+1,a+k+1);
+		    if(solve()) cout<<"YES\n";
+		    else cout<<"NO\n";
+		}
+	}
+    return 0;
+}