Generate a string consisting of characters 'a' and 'b' that satisfy the given conditions
Last Updated :
16 Sep, 2022
Given two integers A and B, the task is to generate and print a string str such that:
- str must only contain the characters 'a' and 'b'.
- str has length A + B and the occurrence of the character 'a' is equal to A and the occurrence of character 'b' is equal to B
- The sub-strings "aaa" or "bbb" must not occur in str.
Note: For the given values of A and B, a valid string can always be generated.
Examples:
Input: A = 1, B = 2
Output: abb
"abb", "bab" and "bba" are all valid strings.
Input: A = 4, B = 1
Output: aabaa
Approach:
- If occurrence(a) > occurrence(b) then append "aab"
- If occurrence(b) > occurrence(a) then append "bba"
- If occurrence(a) = occurrence(b) then append "ab"
Since we reduce the difference between the occurrences of 'a' and 'b' by at most 1 in each iteration so "bba" and "aab" are guaranteed not to be followed by "aab" and "bba" respectively.
Below is the implementation of the above approach:
C++
// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
// Function to generate and print the required string
void generateString(int A, int B)
{
string rt;
while (0 < A || 0 < B) {
// More 'b', append "bba"
if (A < B) {
if (0 < B--)
rt.push_back('b');
if (0 < B--)
rt.push_back('b');
if (0 < A--)
rt.push_back('a');
}
// More 'a', append "aab"
else if (B < A) {
if (0 < A--)
rt.push_back('a');
if (0 < A--)
rt.push_back('a');
if (0 < B--)
rt.push_back('b');
}
// Equal number of 'a' and 'b'
// append "ab"
else {
if (0 < A--)
rt.push_back('a');
if (0 < B--)
rt.push_back('b');
}
}
cout << rt;
}
// Driver code
int main()
{
int A = 2, B = 6;
generateString(A, B);
return 0;
}
// Java implementation of the approach
class GFG
{
// Function to generate and
// print the required string
static void generateString(int A, int B)
{
String rt = "";
while (0 < A || 0 < B)
{
// More 'b', append "bba"
if (A < B)
{
if (0 < B--)
{
rt += ('b');
}
if (0 < B--)
{
rt += ('b');
}
if (0 < A--)
{
rt += ('a');
}
}
// More 'a', append "aab"
else if (B < A)
{
if (0 < A--)
{
rt += ('a');
}
if (0 < A--)
{
rt += ('a');
}
if (0 < B--)
{
rt += ('b');
}
}
// Equal number of 'a' and 'b'
// append "ab"
else
{
if (0 < A--)
{
rt += ('a');
}
if (0 < B--)
{
rt += ('b');
}
}
}
System.out.println(rt);
}
// Driver code
public static void main(String[] args)
{
int A = 2, B = 6;
generateString(A, B);
}
}
// This code is contributed
// by PrinciRaj1992
# Python 3 implementation of the approach
# Function to generate and print
# the required string
def generateString(A, B):
rt = ""
while (0 < A or 0 < B) :
# More 'b', append "bba"
if (A < B) :
if (0 < B):
rt = rt +'b'
B -= 1
if (0 < B):
rt += 'b'
B -= 1
if (0 < A):
rt += 'a'
A -= 1
# More 'a', append "aab"
elif (B < A):
if (0 < A):
rt += 'a'
A -= 1
if (0 < A):
rt += 'a'
A -= 1
if (0 < B):
rt += 'b'
B -= 1
# Equal number of 'a' and 'b'
# append "ab"
else :
if (0 < A):
rt += 'a'
A -= 1
if (0 < B):
rt += 'b'
B -= 1
print(rt)
# Driver code
if __name__ == "__main__":
A = 2
B = 6
generateString(A, B)
# This code is contributed by ita_c
// C# implementation of the approach
using System;
class GFG
{
// Function to generate and
// print the required string
static void generateString(int A, int B)
{
string rt = "";
while (0 < A || 0 < B)
{
// More 'b', append "bba"
if (A < B)
{
if (0 < B--)
{
rt += ('b');
}
if (0 < B--)
{
rt += ('b');
}
if (0 < A--)
{
rt += ('a');
}
}
// More 'a', append "aab"
else if (B < A)
{
if (0 < A--)
{
rt += ('a');
}
if (0 < A--)
{
rt += ('a');
}
if (0 < B--)
{
rt += ('b');
}
}
// Equal number of 'a' and 'b'
// append "ab"
else
{
if (0 < A--)
{
rt += ('a');
}
if (0 < B--)
{
rt += ('b');
}
}
}
Console.WriteLine(rt);
}
// Driver code
public static void Main()
{
int A = 2, B = 6;
generateString(A, B);
}
}
// This code is contributed by Ryuga
<?php
// PHP implementation of the approach
// Function to generate and
// print the required string
function generateString($A, $B)
{
$rt = "";
while (0 < $A || 0 < $B)
{
// More 'b', append "bba"
if ($A < $B)
{
if (0 < $B--)
{
$rt .= ('b');
}
if (0 < $B--)
{
$rt .= ('b');
}
if (0 < $A--)
{
$rt .= ('a');
}
}
// More 'a', append "aab"
else if ($B < $A)
{
if (0 < $A--)
{
$rt .= ('a');
}
if (0 < $A--)
{
$rt .= ('a');
}
if (0 < $B--)
{
$rt .= ('b');
}
}
// Equal number of 'a' and 'b'
// append "ab"
else
{
if (0 < $A--)
{
$rt .= ('a');
}
if (0 < $B--)
{
$rt .= ('b');
}
}
}
echo($rt);
}
// Driver code
$A = 2; $B = 6;
generateString($A, $B);
// This code is contributed
// by Code Mech
?>
<script>
// Javascript implementation of the approach
// Function to generate and
// print the required string
function generateString(A,B)
{
let rt = "";
while (0 < A || 0 < B)
{
// More 'b', append "bba"
if (A < B)
{
if (0 < B--)
{
rt += ('b');
}
if (0 < B--)
{
rt += ('b');
}
if (0 < A--)
{
rt += ('a');
}
}
// More 'a', append "aab"
else if (B < A)
{
if (0 < A--)
{
rt += ('a');
}
if (0 < A--)
{
rt += ('a');
}
if (0 < B--)
{
rt += ('b');
}
}
// Equal number of 'a' and 'b'
// append "ab"
else
{
if (0 < A--)
{
rt += ('a');
}
if (0 < B--)
{
rt += ('b');
}
}
}
document.write(rt);
}
// Driver code
let A = 2, B = 6;
generateString(A, B);
// This code is contributed by avanitrachhadiya2155
</script>
Complexity Analysis:
- Time Complexity: O(Max(a,b))
- Auxiliary Space: O(Max(a,b))
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