pku3670 Eating Together

http://poj.org/problem?id=3670

DP，最长不降子序列，O(n*logn)解法

 #include <stdio.h>
 #define N 30030

 int n, a[N], dp[N];
 const int maxint = (<<)-;

 int bs(int l ,int r, int x)
 {
     int m;
     while(l < r)
     {
         m = (l + r)>>;
         if(dp[m] <= x)
         {
             l = m + ;
         }
         else
         {
             r = m;
         }
     }
     return l;
 }

 int LIS()
 {
     int i, j, maxn = ;
     dp[] = ;
     dp[] = maxint;
     for(i=; i<=n; i++)
     {
         j = bs(, maxn+, a[i]);
         dp[j] = a[i];
         if(j > maxn)
         {
             maxn ++;
             dp[maxn+] = maxint;
         }
     }
     return maxn;
 }

 int main()
 {
     int t, i, j;
     int r1, r2;
     while(~scanf("%d", &n))
     {
         for(i=; i<=n && scanf("%d", a+i); i++);
         r1 = LIS();
         for(i=; i<=n/; i++)
         {
             j = n-i+;
             //printf("%d %d\n", i, j);
             a[i] ^= a[j], a[j] ^= a[i], a[i] ^= a[j];
         }
         r2 = LIS();
         printf("%d\n", n - (r1>r2? r1: r2));
     }
     return ;
 }