Algorithm Problem

Problem_Link

Solution(Time Complexity, Space Complexity)

O(n), O(1)

public static int validString(int N, String S) {

    // Initialize variable 'temp' to 'a' as the 
        // reference for comparison in the string.
    char temp = 'a';

    // Iterate through the length of string S.
    for (int i = 0; i < N; i++) {

        // If the i-th character of S is less than 'temp', 
                //it is not in alphabetical order, so return 0.
        if (temp > S.charAt(i)) return 0;

        // Update 'temp' to the i-th character of S.
        temp = S.charAt(i);
    }

    // If the string is in alphabetical order, return 1.
    return 1;
}