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.

注意是在[1，max(L)]里面找

public class Solution {
    /** 
     *@param L: Given n pieces of wood with length L[i]
     *@param k: An integer
     *return: The maximum length of the small pieces.
     */
    public int woodCut(int[] L, int k) {
        // write your code here
        if (L==null || L.length==0 || k<=0) return 0;
        Arrays.sort(L);
        int l=1, r=L[L.length-1];
        while (l <= r) {
            int m = l+(r-l)/2;
            if (calc(L, m)>=k) l=m+1;
            else r=m-1;
        }
        return r;
    }
    
    public int calc(int[] L, int len) {
        int res = 0;
        for (int i=0; i<L.length; i++) {
            res += L[i]/len;
        }
        return res;
    }
}