找找第k个数在第几堆里

/**
     * 找找第k个数在第几堆里，例如：
     * int k = 25;
     * int[] array = new int[]{10, 12, 14, 15};
     * 答案是 3 .
     *
     * @param heaps
     * @param k
     * @return
     */
    public static int whereAmI(int[] heaps, int k) {
        if (null == heaps || 0 == heaps.length || 0 >= k) {
            return -1;
        }
        int[] heapRecord = new int[heaps.length];
        int sum = 0;
        for (int i = 0; i < heaps.length; i++) {
            sum += heaps[i];
            heapRecord[i] = sum;
        }
        if (k > sum) {
            return -1;
        }
        return 1 + whereAmI(heapRecord, 0, heaps.length - 1, k);
    }

    private static int whereAmI(int[] heapRecord, int start, int end, int k) {
        if (start >= end) {
            return start;
        }
        int mid = start + (end - start) / 2;
        if (heapRecord[mid] == k) {
            return mid;
        }
        if (heapRecord[mid] < k) {
            return whereAmI(heapRecord, mid + 1, end, k);
        }
        return whereAmI(heapRecord, start, mid - 1, k);
    }