题解 | #二分查找-II#

class Solution {
public:
    int find(vector<int>& nums, int target, int left, int right)
    {
        if(left > right)
        {
            return -1;
        }
        int mid = (left + right) / 2;
        if(target == nums[mid])
        {
            return mid;
        }
        else if(target < nums[mid])
        {
            return find(nums, target, left, mid - 1);
        }
        else if(target > nums[mid])
        {
            return find(nums, target, mid + 1, right);
        }
        else
        {
            return -1;
        }
    }
    
    /**
     * 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) {
        // write code here
        int i = find(nums, target, 0, nums.size() - 1);
        while(i > 0 && nums[i - 1] == target)
        {
            i = find(nums, target, 0, i - 1);
        }
        return i;
    }
};