Introduction Link to heading
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:
0 <= A <= 100
0 <= B <= 100
It is guaranteed such an S exists for the given A and B.
Solution Link to heading
State machine solution:
func strWithout3a3b(A int, B int) string {
var sb strings.Builder
lastA, lastB := 0, 0
for i, j := 0, 0; i < A || j < B; {
if (A - i >= B - j && lastA < 2) || lastB == 2 {
sb.WriteRune('a')
i++
lastA++
lastB = 0
} else {
sb.WriteRune('b')
j++
lastA = 0
lastB++
}
}
return sb.String()
}
Explanation Link to heading
Lets keep track counters for last generated a-s and last generated b-s. It is not difficult to build a simple statemachine that will check
switch time-to-time from a generation to b generation.