LeetCode 520. Detect Capital

problem:

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.

first:

class Solution {
    public boolean detectCapitalUse(String word) {
        char[] charArray = word.toCharArray();
        if(Character.isLowerCase(charArray[0])){
            for(char c : charArray){
                if(Character.isUpperCase(c)){
                    return false;
                }
            }
            return true;
        }
        
        if(Character.isUpperCase(charArray[0])&&Character.isUpperCase(charArray[1])){
            for(char c : charArray){
                if(Character.isLowerCase(c)){
                    return false;
                }
            }
            return true;
        }
           
        if(Character.isUpperCase(charArray[0])&&Character.isLowerCase(charArray[1])){
            for(int i=2;i<charArray.length;i++){
                if(Character.isUpperCase(charArray[i])){
                    return false;
                }
            }
            return true;
        }  
           
        return false;   
    }
}

result:

Submission Result: Runtime Error 
Runtime Error Message: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
    at Solution.detectCapitalUse(Solution.java:13)
    at __DriverSolution__.__helper__(__Driver__.java:4)
    at __Driver__.main(__Driver__.java:48)
Last executed input: "G"

second:

class Solution {
    public boolean detectCapitalUse(String word) {
        char[] charArray = word.toCharArray();
        
        if(charArray.length==1){
            return true;
        }
        
        if(Character.isLowerCase(charArray[0])){
            for(char c : charArray){
                if(Character.isUpperCase(c)){
                    return false;
                }
            }
            return true;
        }
        
        if(Character.isUpperCase(charArray[0])&&Character.isUpperCase(charArray[1])){
            for(char c : charArray){
                if(Character.isLowerCase(c)){
                    return false;
                }
            }
            return true;
        }
           
        if(Character.isUpperCase(charArray[0])&&Character.isLowerCase(charArray[1])){
            for(int i=2;i<charArray.length;i++){
                if(Character.isUpperCase(charArray[i])){
                    return false;
                }
            }
            return true;
        }  
           
        return false;   
    }
}

result:

discussion里得票最高的写法：

public class Solution {
    public boolean detectCapitalUse(String word) {
        int cnt = 0;
        for(char c: word.toCharArray()) if('Z' - c >= 0) cnt++;
        return ((cnt==0 || cnt==word.length()) || (cnt==1 && 'Z' - word.charAt(0)>=0));
    }
}

result：

third try:

class Solution {
    public boolean detectCapitalUse(String word) {
        char[] charArray = word.toCharArray();
        
        if(charArray.length==1){
            return true;
        }
        
        if(!(0<='Z'-charArray[0])){
            for(char c : charArray){
                if(0<='Z'-c){
                    return false;
                }
            }
            return true;
        }
        
        if(0<='Z'-charArray[0]&&0<='Z'-charArray[1]){
            for(char c : charArray){
                if(!(0<='Z'-c)){
                    return false;
                }
            }
            return true;
        }
           
        if(0<='Z'-charArray[0]&&!(0<='Z'-charArray[1])){
            for(int i=2;i<charArray.length;i++){
                if(0<='Z'-charArray[i]){
                    return false;
                }
            }
            return true;
        }  
           
        return false;   
    }
}

result:

Conclusion:

 可见Character.isUpperCase(char c)方法效率较低。其实现留待后续查看。