Leetcode - Search for a Range

My code:

public class Solution {
    public int[] searchRange(int[] nums, int target) {
        if (nums == null || nums.length == 0)
            return null;
        int[] result = new int[2];
        int lo = 0;
        int hi = nums.length - 1;
        BinarySearch(lo, hi, target, nums, result);
        return result;
    }
    
    private void BinarySearch(int lo, int hi, int target, int[] nums, int[] result) {
        if (lo > hi) {
            result[0] = -1;
            result[1] = -1;
            return;
        }
        
        int mid = (lo + hi) / 2;
        if (target > nums[mid]) {
            while (mid + 1 < nums.length && nums[mid + 1] == nums[mid])
                mid++;
            BinarySearch(mid + 1, hi, target, nums, result);
        }
        else if (target < nums[mid]) {
            while (mid - 1 >= 0 && nums[mid - 1] == nums[mid])
                mid--;
            BinarySearch(lo, mid - 1, target, nums, result);
        }
        else {
            int i = mid;
            while (i + 1 < nums.length && nums[i + 1] == nums[i])
                i++;
            result[1] = i;
            i = mid;
            while (i - 1 >= 0 && nums[i - 1] == nums[i])
                i--;
            result[0] = i;
        }
    }
}

My test result:

这道题目没什么大的难度。主要就是其中需要用 while循环过滤掉那些重复出现的数字，之前一道题目中出现过一种方法。具体忘了。

**
总结：binary search in range
**

Anyway, Good luck, Richardo!

原先的做法并不能保证严格的O(log n).
还是得用两次bianry search
第一次，搜索 target 出现的左边界，相比于BS来说，变化在于，
when nums[mid] == target:
mid--;
第二次，搜索target出现的右边界，相比于BS来说，变化在于：
when nums[mid] == target:
mid++;

而且，最后给ret赋值的时候，得注意判断，
begin是否 end时候 >= 0

Anyway, Good luck, Richardo! -- 09/03/2016

My code:

public class Solution {
    public int[] searchRange(int[] nums, int target) {
        if (nums == null || nums.length == 0) {
            return new int[]{-1, -1};
        }
        
        int[] ret = new int[2];
        int start = 0;
        int end = nums.length - 1;
        while (start + 1 < end) {
            int mid = start + (end - start) / 2;
            if (nums[mid] == target) {
                end = mid;
            }
            else if (nums[mid] < target) {
                start = mid;
            }
            else {
                end = mid;
            }
        }
        if (nums[start] == target) {
            ret[0] = start;
        }
        else if (nums[end] == target) {
            ret[0] = end;
        }
        else {
            ret[0] = -1;
            ret[1] = -1;
            return ret;
        }
        
        start = 0;
        end = nums.length - 1;
        while (start + 1 < end) {
            int mid = start + (end - start) / 2;
            if (nums[mid] == target) {
                start = mid;
            }
            else if (nums[mid] > target) {
                end = mid;
            }
            else {
                start = mid;
            }
        }
        
        if (nums[end] == target) {
            ret[1] = end;
        }
        else if (nums[start] == target) {
            ret[1] = start;
        }
        else {
            ret[0] = -1;
            ret[1] = -1;
            return ret;
        }
        
        return ret;
    }
}

reference:
http://www.jiuzhang.com/solutions/search-for-a-range/

Anyway, Good luck, Richardo! -- 10/16/2016