class Solution {

    /**

     * @param nums: The integer array.

     * @param target: Target to find.

     * @return: The first position of target. Position starts from 0.

     */

    public int binarySearch(int[] nums, int target) {

        if(nums == null) return -1;

        if(nums.length == 0) return -1;

        int left = 0; int right = nums.length -1; 

        while(left + 1 < right){

            int mid = (left + right) / 2;

            if(nums[mid] < target){

                left = mid;

            }

            else if(nums[mid] > target){

                right = mid;

            }

            else if(nums[mid] == target){

                right = mid;

            }

        }

        if(nums[left] == target){

            return left;

        }

        else if(nums[right] == target){

            return right;

        }

        else return -1;

    }

}