解题思路：

这题可以直接运用位运算解得

代码：

Python

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def countConsistentStrings(allowed: str, words: list[str]) -> int:
    mask = 0
    for c in allowed:
        mask |= 1 << (ord(c) - ord('a'))
    res = 0
    for word in words:
        mask1 = 0
        for c in word:
            mask1 |= 1 << (ord(c) - ord('a'))
        res += (mask | mask1) == mask
    return res

C++

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class Solution {
public:
    int countConsistentStrings(string allowed, vector<string>& words) {
        int mask = 0;
        for (auto c: allowed) {
            mask |= 1 << (c - 'a');
        }
        
        int res = 0;
        for (auto word: words) {
            int mask1 = 0;
            for (auto c: word) {
                mask1 |= 1 << (c - 'a');
            }
            if ((mask | mask1) == mask) ++res;
        }
        return res;
    }
};