LC 774. Minimize Max Distance to Gas Station 【lock，hard】

On a horizontal number line, we have gas stations at positions stations[0], stations[1], ..., stations[N-1], where N = stations.length.

Now, we add K more gas stations so that D, the maximum distance between adjacent gas stations, is minimized.

Return the smallest possible value of D.

Example:

Input: stations = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], K = 9
Output: 0.500000

Note:

1. stations.length will be an integer in range [10, 2000].
2. stations[i] will be an integer in range [0, 10^8].
3. K will be an integer in range [1, 10^6].
4. Answers within 10^-6 of the true value will be accepted as correct.

也是用了二分查找，找的是中位数。

 

Runtime:28ms  Beats: 81.77%

class Solution {
public:
    double minmaxGasDist(vector<int>& stations, int K) {
        double left = 0.0, right = 1000000.0, mid = 0.0;
        while (left + 0.0000001 < right) {
            mid = left + (right - left) / 2.0;
            int cnt = 0;
            for (int i = 0; i < stations.size() - 1; i++) {
                cnt += (stations[i + 1] - stations[i]) / mid;
            }
            if (cnt <= K) right = mid;
            else left = mid;
        }
        return left;
    }
};