Codevs 1058 合唱队形 ---2004年NOIP全国联赛提高组 dp

#include <cstdio>
#include <cstring>
#include <iostream>
#include <cstdlib>
#include <algorithm>
using namespace std;

#define MAXN (100+10)
int a[MAXN], dp[MAXN], za[MAXN];

#define INF (1e9)

int main()
{
int n;
cin >> n;
for(int i = 1, j = n; i <= n && j >= 1; i ++, j --)
scanf("%d", &a[i]), za[j] = a[i];

bool up = 0, down = 0;
for(int i = 1; i < n; i ++)
if(a[i] < a[i+1]) down = 1;
else if(a[i] > a[i+1]) up = 1;

if((up && !down) || (down && !up))
{
puts("0");
return 0;
}

int ans = 0;
for(int nn = 2; nn < n; nn ++)
{
int cnt = 0;
fill(dp+1, dp+n+1, INF);

for(int i = 1; i < nn; i ++)
if(a[i] < a[nn])
dp[lower_bound(dp+1, dp+n+1, a[i])-dp] = a[i];

cnt += (lower_bound(dp+1, dp+n+1, INF)-dp-1);

fill(dp+1, dp+n+1, INF);

for(int i = 1; i < n-nn+1; i ++)
if(za[i] < za[n-nn+1])
dp[lower_bound(dp+1, dp+n+1, za[i])-dp] = za[i];

cnt += (lower_bound(dp+1, dp+n+1, INF)-dp-1);
cnt ++;

ans = max(ans, cnt);
}

cout << n-ans << endl;

return 0;
}

/*
输入数据 (显示前20行)
20
130 140 150 160 170 180 190 200 210 220 221 222 223 224 225 226 227 228 229 230
你的答案
< 1
正确答案
> 0

*/