洛谷 P2896 [USACO08FEB]Eating Together S

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Problem-solving ideas:

Seeking again does not decrease and no increase in the longest sub-sequence, then subtracting the total length of greater length.

AC Code:

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<algorithm>
 4 
 5 using namespace std;
 6 
 7 int n,a[30001],f[30001],dp[30001],len,tot;
 8 
 9 int main() {
10     scanf("%d",&n);
11     for(int i = 1;i <= n; i++)
12         scanf("%d",&a[i]);
13     f[++len] = a[1];
14     for(int i = 2;i <= n; i++) {
15         if(a[i] >= f[len]) {
16             f[++len] = a[i];
17             continue;
18         }
19         int u = upper_bound(f+1,f+len+1,a[i]) - f;
20         f[u] = a[i];
21     }
22     dp[++tot] = a[1];
23     for(int i = 2;i <= n; i++) {
24         if(a[i] <= dp[tot]) {
25             dp[++tot] = a[i];
26             continue;
27         }
28         int u = upper_bound(dp+1,dp+len+1,a[i],greater<int>()) - dp;
29         dp[u] = a[i]; 
30     }
31     printf("%d",n - max(tot,len));
32     return 0;
33 }