[LeetCode] Detect Capital 檢測大寫格式

 

Given a word, you need to judge whether the usage of capitals in it is right or not.

We define the usage of capitals in a word to be right when one of the following cases holds:

1. All letters in this word are capitals, like "USA".
2. All letters in this word are not capitals, like "leetcode".
3. Only the first letter in this word is capital if it has more than one letter, like "Google".

Otherwise, we define that this word doesn't use capitals in a right way.

Example 1:

Input: "USA"
Output: True

Example 2:

Input: "FlaG"
Output: False

Note: The input will be a non-empty word consisting of uppercase and lowercase latin letters.

 

這道題給了我們一個單詞，讓我們檢測大寫格式是否正確，規定了三種正確方式，要么都是大寫或小寫，要么首字母大寫，其他情況都不正確。那么我們要做的就是統計出單詞中所有大寫字母的個數cnt，再來判斷是否屬於這三種情況，如果cnt為0，說明都是小寫，正確；如果cnt和單詞長度相等，說明都是大寫，正確；如果cnt為1，且首字母為大寫，正確，其他情況均返回false，參見代碼如下：

 

解法一：

class Solution {
public:
    bool detectCapitalUse(string word) {
        int cnt = 0, n = word.size();
        for (int i = 0; i < n; ++i) {
            if (word[i] <= 'Z') ++cnt;
        }
        return cnt == 0 || cnt == n || (cnt == 1 && word[0] <= 'Z');
    }
};

 

下面這種方法利用了STL的內置方法count_if，根據條件來計數，這樣使得code非常簡潔，兩行就搞定了，喪心病狂啊～

 

解法二：

class Solution {
public:
    bool detectCapitalUse(string word) {
        int cnt = count_if(word.begin(), word.end(), [](char c){return c <= 'Z';});
        return cnt == 0 || cnt == word.size() || (cnt == 1 && word[0] <= 'Z');
    }
};

 

參考資料：

https://discuss.leetcode.com/topic/79912/3-lines

https://discuss.leetcode.com/topic/79930/java-1-liner

https://discuss.leetcode.com/topic/80314/6ms-2-lines-c-solution/2

https://discuss.leetcode.com/topic/79911/simple-java-solution-o-n-time-o-1-space

 

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