> For the complete documentation index, see [llms.txt](https://hao-fu-1.gitbook.io/oj/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hao-fu-1.gitbook.io/oj/search/topological-sort/269.-alien-dictionary/953.-verifying-an-alien-dictionary.md).

# 953. Verifying an Alien Dictionary

给定字符串order表示字符先后顺序，问一组词是否按照order定义的顺序排序。是Alien Dict那道题反过来，思路类似，依次检查相邻的两个word找出第一个不同的字符，然后看是否符合order定义。为了方便查找字符的顺序，用一个map存字符和它的ranking。当没有字符不同时，再检测是否满足长度长的排后面。

```cpp
/*
 * @lc app=leetcode id=953 lang=cpp
 *
 * [953] Verifying an Alien Dictionary
 */

// @lc code=start
class Solution {
public:
    bool isAlienSorted(vector<string>& words, string order) {
        unordered_map<char, int> o;
        for (int i = 0; i < order.length(); ++i) {
            o[order[i]] = i;
        }
        for (int i = 1; i < words.size(); ++i) {
            const auto s = words[i - 1], t = words[i];
            bool found = false;
            for (int j = 0; j < min(s.length(), t.length()); ++j) {
                if (s[j] != t[j]) {
                    if (o[s[j]] > o[t[j]]) return false;
                    found = true;
                    break;
                }
            }
            if (!found && s.length() > t.length()) return false; 
        }
        return true;
    }
};
// @lc code=end


```


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