detect-capital

Detect Capital – LeetCode 520

Problem

Description

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:

• All letters in this word are capitals, like “USA”.

• All letters in this word are not capitals, like “leetcode”.

• 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.

Answer

Original

Code

class Solution {
public:
    bool detectCapitalUse(string word) {
        if(word[0] <= 'z' && word[0] >= 'a'){
            for(auto p = word.cbegin(); p != word.cend(); ++p){
                if(*p <= 'Z' && *p >= 'A')
                    return false;
            }
            return true;
        } else {
            if(word.size() == 1)
                return true;
            if(word[1] <= 'z' && word[1] >= 'a'){
                for(auto p = word.cbegin()+1; p != word.cend(); ++p){
                if(*p <= 'Z' && *p >= 'A')
                    return false;
                }
                return true;
            } else {
                for(auto p = word.cbegin()+1; p != word.cend(); ++p){
                if(*p <= 'z' && *p >= 'a')
                    return false;
                }
                return true;
            }
        }
    }
};

思路

简单的枚举情况。时间复杂度$O(n)$，空间复杂度$O(1)$。
耗时$15$ ms，排名$42.53\%$

Better

思路

漂亮的枚举反面情况。时间复杂度$O(n)$，空间复杂度$O(1)$。
耗时$13$ ms，排名$22.82\%$

Code

class Solution {
public:
    bool detectCapitalUse(string word) {
        for(int i = 1; i < word.size(); i++)
        {
            if(isupper(word[i]) && islower(word[i-1]))
                return false;
            if(islower(word[i]) && isupper(word[i-1]) && i!=1)
                return false;
        }
        return true;
    }
};