QUESTION:
Given a string s consisting of only the characters ‘a’ and ‘b’, return true if every ‘a’ appears before every ‘b’ in the string. Otherwise, return false.
Example 1:
Input: s = "aaabbb"
Output: true
Explanation:
The 'a's are at indices 0, 1, and 2, while the 'b's are at indices 3, 4, and 5.
Hence, every 'a' appears before every 'b' and we return true.
Example 2:
Input: s = "abab"
Output: false
Explanation:
There is an 'a' at index 2 and a 'b' at index 1.
Hence, not every 'a' appears before every 'b' and we return false.
Example 3:
Input: s = "bbb"
Output: true
Explanation:
There are no 'a's, hence, every 'a' appears before every 'b' and we return true.
Constraints:
1 <= s.length <= 100
s[i] is either 'a' or 'b'.
EXPLANATION:
easy的题目, 一个for循环就行.
SOLUTION:
class Solution {
func checkString(_ s: String) -> Bool {
var result:Bool = true
var arr:[Character] = Array(s)
for index in stride(from: 1, to: s.count, by: 1) {
if arr[index].asciiValue! < arr[index-1].asciiValue! {
return false
}
}
return result
}
}