[프로그래머스] 문자열 섞기

class Solution {
    public String solution(String str1, String str2) {
        char[] char1 = str1.toCharArray();
        char[] char2 = str2.toCharArray();

        StringBuilder sb = new StringBuilder();
        for (int i=0; i<char1.length; i++) {
            sb.append(char1[i]).append(char2[i]);
        }

        return sb.toString();
    }
}

Stringbuilder**

1. 길이가 같은 두 문자열인점 활용
2. append로 두개씩 붙임

[charAt으로 하나하나 글자 떼오기]

class Solution {
    public String solution(String str1, String str2) {
        String answer = "";

        for(int i = 0; i < str1.length(); i++){
            answer+= str1.charAt(i);
            answer+= str2.charAt(i);
        }

        return answer;
    }
}

[Stringbuffer 사용]

import java.util.*;

class Solution {
    public String solution(String str1, String str2) {
        StringBuffer sb = new StringBuffer();
        for (int i = 0;i < str1.length();i++)
            sb.append(str1.charAt(i)).append(str2.charAt(i));
        return sb.toString();
    }
}