NC16664 合唱队形

从左往右求最长上升子序列，在从右往左求最长上升子序列。

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
const int maxn = 105;
int arr[maxn];
vector<int>nums(maxn);
int dp[maxn];
int dp2[maxn];
int main()
{
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> arr[i];
        nums[i] = arr[i];
    }

    for (int i = 1; i <= n; i++) {
        dp[i] = 1;
        for (int j = 1; j < i; j++) {
            if (arr[j] < arr[i]) {
                dp[i] = max(dp[j] + 1, dp[i]);
            }
        }
    }
    reverse(nums.begin() + 1, nums.begin() + 1 + n);
    for (int i = 1; i <= n; i++) {
        dp2[i] = 1;
        for (int j = 1; j < i; j++) {
            if (nums[j] < nums[i]) {
                dp2[i] = max(dp2[j] + 1, dp2[i]);
            }
        }
    }
    int ans = 0;
    for (int i = 1; i <= n; i++) {
      ans=max(dp[i]+dp2[n-i+1]-1,ans);
    }
    cout << n-ans;

    /*错误的for循环，请思考一下这两个for循环有什么不同
         int ans = 0x3f;
    for (int i = 1; i <= n; i++) {
        int temp = dp[i] + dp2[n - i];
        ans = min(ans, n - temp);
    }
    cout << ans;
    */
}