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.

Example For L=[232, 124, 456], k=7, return 114.

Notes:

• Binary Search on Result
• The piece must be between 1 and the largest piece
• Choose the middle piece, calculate the number with this piece size to cut the woods (Binary Search)
• Change start/end according to the comparison between number and k.
• Find the maximum length, so don't stop when meet k, continue to find bigger one

Time: O(nLogLength)

    public int woodCut(int[] L, int k) {
        if (L == null || L.length == 0) {
            return 0;
        }

        // find the largest one
        int end = findLargest(L);
        int start = 1;

        while(start + 1 < end) {
            int middle = start + (end-start)/2;
            int num = cut(L, middle);
            if (num >= k) {
                start = middle;
            } else {
                end = middle;
            }
        }

        if (cut(L, end) >= k) {
            return end;
        }

        if (cut(L, start) >= k) {
            return start;
        }

        return 0;
    }

    private int findLargest(int[] L) {
        int largest = L[0];
        for (int i = 1; i < L.length; ++i) {
            largest = Math.max(largest, L[i]);
        }

        return largest;
    }

    private int cut(int[] L, int l) {
        int num = 0;
        for (int i = 0; i < L.length; ++i) {
            num += L[i]/l;
        }

        return num;
    }