cf 448 C. Painting Fence

#include<bits/stdc++.h>
using namespace std;
int h[5010];
const int INF=1e9+7;
int cal(int l,int r)
{
    if(l>r)
      return 0;
    int minn=INF;
    for(int i=l;i<=r;i++)
       minn=min(h[i],minn);
    for(int i=1;i<=r;i++)
       h[i]-=minn;
    int now=minn;
    int s=l;
    for(int i=l;i<=r;i++)
    {
        if(i==r&&h[i]>0)//注意这里要加特判，最后一位必须大于0，否则可能一直递归下去 
        {
            now+=cal(s,i);
        }
        else if(h[i]==0)
        {
            now+=cal(s,i-1),s=i+1;
        }
    }
    return min(r-l+1,now);
}
int main()
{
    int n;
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
       scanf("%d",&h[i]);
    printf("%d\n",cal(1,n));
}