LC 984. String Without AAA or BBB

Given two integers A and B, return any string S such that:

• S has length A + B and contains exactly A 'a' letters, and exactly B 'b' letters;
• The substring 'aaa' does not occur in S;
• The substring 'bbb' does not occur in S.

Example 1:

Input: A = 1, B = 2
Output: "abb"
Explanation: "abb", "bab" and "bba" are all correct answers.

Example 2:

Input: A = 4, B = 1
Output: "aabaa"

Note:

1. 0 <= A <= 100
2. 0 <= B <= 100
3. It is guaranteed such an S exists for the given A and B.

Runtime:  0 ms, faster than 100.00% of C++ online submissions for String Without AAA or BBB.

Memory Usage:  753.7 KB, less than 100.00% of C++ online submissions for String Without AAA or BBB.

class Solution {
public:
  string strWithout3a3b(int A, int B) {
    if(A <= B) {
      return helper("b","a", B, A);
    }
    return helper("a","b", A, B);
  }

  string helper(string more, string less, int m, int l){
    string ret = "";
    if( m - l > l) {
      //assert(m - l <= 3);
      for(int i=0; i<l; i++){
        ret += more + more + less;
      }
      for(int i=0; i< m - l - l; i++) {
        ret += more;
      }
    }
    else {
      for(int i=0; i<m-l; i++) {
        ret += more + more + less;
      }
      for(int i=0; i<2*l-m; i++){
        ret += more + less;
      }
    }
    return ret;
  }

};