34. Search for a Range

就是二分搜索，做三遍。

1.第一遍找到第一个target

2.第二遍找到左侧的边界

3.第三遍找到右侧的边界

 

    public int[] searchRange(int[] nums, int target) {
        int[] res = new int[2];
        res[0] = -1;
        res[1] = -1;
        if(nums == null || nums.length == 0) {
            return res;
        }
        int low = 0;
        int high = nums.length - 1;
        int mid = 0;
        boolean found = false;
        while(low <= high) {
            mid = low + (high - low) / 2;
            if(nums[mid] == target) {
                found = true;
                break;
            } else if(nums[mid] > target) {
                high = mid - 1;
            } else {
                low = mid + 1;
            }
        }
        if(found == true) {
            int l = mid;
            int r = nums.length - 1;
            int m = 0;
            while(l <= r) {
                m = l + (r - l) / 2;
                if(nums[m] == target) {
                    l = m + 1;
                } else {
                    r = m - 1;
                }
            }
            res[1] = r;
            l = 0; 
            r = m;
            while(l <= r) {
                m = l + (r - l) / 2;
                if(nums[m] == target)  {
                    r = m - 1;
                } else {
                    l = m + 1;
                }
            }
            res[0] = l;
        }
        return res;
    }