题解 | #二分查找-II#

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 如果目标值存在返回下标，否则返回 -1
     * @param nums int整型一维数组 
     * @param target int整型 
     * @return int整型
     */
    public int search (int[] nums, int target) {
        // write code here
        if(nums  == null || nums.length == 0){
            return -1;
        }
        int left = 0;
        int right = nums.length - 1;
        while(left <= right){
            int mid = (right - left) / 2 +left;
            if(nums[mid] > target){
                right = mid - 1;
            }else if(nums[mid] < target){
                left = mid +1;
            }else{
                if(mid == 0 || (mid - 1 >= 0 && nums[mid-1] != target)){
                    return mid;
                }else{
                    right = mid -1;
                }
            }
        }
        return -1;
    }
}