520. Detect Capital

/**
520. Detect Capital
https://leetcode.com/problems/detect-capital/
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, like "Google".
Given a string word, return true if the usage of capitals in it is right.

Example 1:
Input: word = "USA"
Output: true

Example 2:
Input: word = "FlaG"
Output: false

Constraints:
1. 1 <= word.length <= 100
2. word consists of lowercase and uppercase English letters.
*/

pub struct Solution {}

impl Solution {
    /*
    Solution: check letter by rule given by topic, Time:O(n), Space:O(n)
    */
    pub fn detect_capital_use(word: String) -> bool {
        let mut words = word.chars();
        //check if all the lower case;
        if (words.all(|x| x.is_lowercase())) {
            return true;
        }
        //check if all the upper case;
        if (words.all(|x| x.is_uppercase())) {
            return true;
        }
        /*
        check if first word is upper case and other is lower case
        */
        let mut words2 = word.chars();
        if words2.enumerate().all(|(id, c)| {
            if (id == 0) {
                c.is_uppercase()
            } else {
                c.is_lowercase()
            }
        }) {
            return true;
        }
        false
    }
}