srm624D1E.cpp

#include <algorithm>
#include <vector>
using namespace std;
class BuildingHeights {
public:
	int minimum(vector <int> heights) {
		const int N = heights.size();
		sort(heights.begin(),heights.end());
		vector<int> accum(N);
		accum[0] = heights[0];
		for (int i = 1; i < N; i++)
			accum[i] = accum[i-1]+heights[i];
		int ans = 0;
		for (int i = 2; i <= N; i++) {
			int now = 1e9;
			for (int j = 0; i+j-1 < N; j++)
				now = min(now,heights[j+i-1]*i-(accum[j+i-1]-(j?accum[j-1]:0)));
			ans ^= now;
		}
		return ans;
	}
};