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:

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

这道题的贪心思想还是很明显的，首先判断A,B的大小，若A大于等于B，检查当前字符串res末尾是否已有两个连续的A，若有则插入b，同时B–；否则插入a，同时A–。B大于A时同理。

class Solution {
public:
    string strWithout3a3b(int A, int B) {
        string res;
        while(A>0||B>0)
        {
            if(A>=B)
            {
                if(res.size()>=2&&res[res.size()-1]=='a'&&res[res.size()-2]=='a') res+='b',B--;
                else res+='a',A--;
            }
            else
            {
                if(res.size()>=2&&res[res.size()-1]=='b'&&res[res.size()-2]=='b') res+='a',A--;
                else res+='b',B--;
            }
        }
        return res;
    }
};