【一次过】Lintcode 1193. Detect Capital

本文介绍了一种用于判断字符串中大小写使用是否正确的算法。该算法主要针对三种合法情况：全大写如USA；全小写如leetcode；仅首字母大写如Google。通过分析字符串的首个字符及其后续字符的状态来实现，适用于由英文字母组成的非空字符串。

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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.

样例

Input: "USA"
Output: True

Input: "FlaG"
Output: False

注意事项

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

解题思路：

说了这么多，只需考虑情况三种情况，具体见下：

public class Solution {
    /**
     * @param word: a string
     * @return: return a boolean
     */
    public boolean detectCapitalUse(String word) {
        // write your code here
        if(word == null || word.length() == 0)
            return false;
            
        if(Character.isUpperCase(word.charAt(0))){ //如果首位为大写，则分为以下两种情况
            if(word.length()>=2 && Character.isLowerCase(word.charAt(1))){//如果首位大写，第二位为小写的情况
                for(int i=2 ; i<word.length() ; i++){
                    if(!Character.isLowerCase(word.charAt(i)))
                        return false;
                }
            }else if(word.length()>=2 && Character.isUpperCase(word.charAt(1))){//如果首位大写，第二位大写的情况
                for(int i=2 ; i<word.length() ; i++){
                    if(!Character.isUpperCase(word.charAt(i)))
                        return false;
                }
            }
            
            return true;
        }else if(Character.isLowerCase(word.charAt(0))){ //如果首位小写的情况
            for(int i=1 ; i<word.length() ; i++){
                if(!Character.isLowerCase(word.charAt(i)))
                    return false;
            }
            
            return true;
        }else //其他情况
            return false;
    }
}