LintCode Wood Cut

Given n pieces of wood with length L[i] (integer array). Cut them into small pieces to guarantee you could have equal or more than k pieces with the same length. What is the longest length you can get from the n pieces of wood? Given L & k, return the maximum length of the small pieces.
Have you met this question in a real interview? Yes
Example
For L=[232, 124, 456], k=7, return 114.
Note
You couldn't cut wood into float length.
Challenge
O(n log Len), where Len is the longest length of the wood.

这个好像在挑战编程里看到过类似的，用二分搜索，用upper_bound的思想，注意除零的情况。

class Solution {
public:
    /**
     *@param L: Given n pieces of wood with length L[i]
     *@param k: An integer
     *return: The maximum length of the small pieces.
     */
    int woodCut(vector<int> L, int k) {
        // write your code here
        long lo = 0;
        long hi = 0;
        for (int e : L) {
            if (hi < e) {
                hi = e;
            }
        }
        
        hi++;
        while (lo < hi) {
            long mid = (lo + hi) / 2;
            if (mid == 0) {
                return 0;
            }
            long tryK = pieces(L, mid);
            if (tryK >= k) {
                lo = mid + 1;
            } else {
                hi = mid;
            }
        }
        
        return lo - 1;
    }
    
    long pieces(vector<int>& L, long len) {
        int count = 0;
        for (int e : L) {
            count += e / len;
        }
        return count;
    }
};