Find longest common prefix?

Question

In two strings:

"Mary Had a Little Lamb"
"Mary Had a Big Lamb"

should return

"Mary Had a "

Answer 1

You don't need to use a StringBuilder - just return the substring:

public String greatestCommonPrefix(String a, String b) {
    int minLength = Math.min(a.length(), b.length());
    for (int i = 0; i < minLength; i++) {
        if (a.charAt(i) != b.charAt(i)) {
            return a.substring(0, i);
        }
    }
    return a.substring(0, minLength);
}