codeforces 448C 分治

#include<iostream>
#include<algorithm>
#define INF 0x3f3f3f
using namespace std;

const int maxn = 5005;
int h[maxn];

int solve(int l, int r)
{
	int Min = INF;
	int sum, flag = l;
	for (int i = l; i <=r; i++) {
		Min = min(Min, h[i]);
	}
	for (int i = l; i <=r; i++)h[i] -= Min;
	sum = Min;
	for (int i = l; i <=r; i++) {
		if (h[i] == 0) {
			if (flag == i) {
				flag++;
				continue;
			}
			sum += solve(flag, i - 1);
			flag = i + 1;
		}
	}
	if (h[r] != 0)sum += solve(flag, r);
	sum = min(sum, r - l + 1);
	return sum;
}

int main()
{
	int n;
	cin >> n;
	for (int i = 1; i <=n; i++)
		cin >> h[i];
	int ans = solve(1, n);
	cout << ans<< endl;
	return 0;
}