leetcode 1832. Check if the Sentence Is Pangram（判断句子是否是全字母）

A pangram is a sentence where every letter of the English alphabet appears at least once.

Given a string sentence containing only lowercase English letters, return true if sentence is a pangram, or false otherwise.

Example 1:

Input: sentence = “thequickbrownfoxjumpsoverthelazydog”
Output: true
Explanation: sentence contains at least one of every letter of the English alphabet.
Example 2:

Input: sentence = “leetcode”
Output: false

判断句子sentence中，是否含有所有的26个字母。

思路：

可用一个数组记录每个字母出现的次数，最后看是否有未出现的字母，如果有，返回false

public boolean checkIfPangram(String sentence) {
    int[] cnt = new int[26];
    
    for(int i = 0; i < sentence.length(); i++) {
        cnt[sentence.charAt(i) - 'a'] ++;
    }
    
    for(int i = 0; i < 26; i++) {
        if(cnt[i] == 0) return false;
    }
    
    return true;
}

上面这个方法要遍历一遍sentence,
然而字母只有26个，是不是只需要判断26个字母是否出现就可以了。
这样就只需要遍历26个字母。

public boolean checkIfPangram(String sentence) {
    
    for(int i = 0; i < 26; i++) {
        if(sentence.indexOf(i + 'a') == -1) return false;
    }
    
    return true;
}