NC105：二分查找-II

res=-1，首先找到中间的数

1. nums[mid]==target说明右边都是>=target的数、更新res,right=mid-1
2. nums[mid]>target说明右边都是>target的数,right=mid-1
3. nums[mid]<target说明左边都是<target的数,left=mid+1;

   public int search (int[] nums, int target) {
        // write code here
        if(nums.length==0){
            return -1;
        }
        int res=-1;
        int left=0,right=nums.length-1;
        if(nums[left]>target || nums[right]<target ){
            return -1;
        }
        while(left<=right){
            int mid=(right-left)/2+left;
            if(nums[mid]==target){
                res=mid;
                right=mid-1;
            }
            else if(nums[mid]>target){
                right=mid-1;
            }
            else{
                left=mid+1;
            }
        }
        return res;
    }