题解 | #二分查找-II#

class Solution {
public:
    /**
     * 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vector 
     * @param target int整型 
     * @return int整型
     */
    int search(vector<int>& nums, int target) 
    {
        int nRet = -1;
        int left = 0;
        int right = nums.size();
        if(right == 0)return -1;
        int mid = (right + left) / 2;
        for(int i = mid; i <= right && i >= left;)
        {
            if(nums[i] == target)
            {
                nRet = i;
                i--;
                continue;
            }
            else if(nums[i] < target)
            {
                if(nRet != -1)break;
                left = i + 1;
            }
            else if(nums[i] > target)
            {
                if(nRet != -1)break;
                right = i - 1;
            }
            i = (right + left) / 2;
        }
        return nRet;
    }
};