设up[i][j]为第i位升序为j的最小修改数，down为降序

#include
    
     #include
     
      using namespace std;int n,a[30005],up[30005][4],down[30005][4];int main(){    scanf("%d",&n);    for(int i=1;i<=n;i++)    {        scanf("%d",&a[i]);        up[i][3]=min(up[i-1][1],min(up[i-1][2],up[i-1][3]))+1;        up[i][2]=min(up[i-1][1],up[i-1][2])+1;        up[i][1]=up[i-1][1]+1;        up[i][a[i]]--;        down[i][1]=min(down[i-1][1],min(down[i-1][2],down[i-1][3]))+1;        down[i][2]=min(down[i-1][2],down[i-1][3])+1;        down[i][3]=down[i-1][3]+1;        down[i][a[i]]--;    }    int ans=up[n][1];    for(int i=1;i<=3;i++)        ans=min(ans,min(up[n][i],down[n][i]));    printf("%d\n",ans);    return 0;}