LeetCode 1233. 删除子文件夹

示例 1：
输入：folder = ["/a","/a/b","/c/d","/c/d/e","/c/f"]
输出：["/a","/c/d","/c/f"]
解释："/a/b/" 是 "/a" 的子文件夹，而 "/c/d/e" 是 "/c/d" 的子文件夹。

示例 2：
输入：folder = ["/a","/a/b/c","/a/b/d"]
输出：["/a"]
解释：文件夹 "/a/b/c" 和 "/a/b/d/" 都会被删除，因为它们都是 "/a" 的子文件夹。

示例 3：
输入：folder = ["/a/b/c","/a/b/d","/a/b/ca"]
输出：["/a/b/c","/a/b/ca","/a/b/d"]
 
提示：
1 <= folder.length <= 4 * 10^4
2 <= folder[i].length <= 100
folder[i] 只包含小写字母和 /
folder[i] 总是以字符 / 起始
每个文件夹名都是唯一的

class Solution {
public:
    vector<string> removeSubfolders(vector<string>& folder) {
        sort(folder.begin(), folder.end());
        vector<string> ans(1,folder[0]);
        string str = folder[0]+"/";//便于查找 "/a/b/c","/a/b/ca"
        for(int i = 1; i < folder.size(); ++i)
        {
        	while(i < folder.size() && folder[i].find(str) != folder[i].npos)
	        	i++;//是前面的子文件夹，继续往后查
	        if(i < folder.size())//不是前面文件夹的子文件夹
	        {
	        	ans.push_back(folder[i]);//加入答案
	        	str = ans.back()+"/";//更新后面查找的参考文件夹
	        }
        }
        return ans;
    }
};