Maximum number of characters between any two same character in a string
Last Updated :
19 Aug, 2022
Given a string, find the maximum number of characters between any two characters in the string. If no character repeats, print -1.
Examples:
Input : str = "abba"
Output : 2
The maximum number of characters are
between two occurrences of 'a'.
Input : str = "baaabcddc"
Output : 3
The maximum number of characters are
between two occurrences of 'b'.
Input : str = "abc"
Output : -1
Approach 1 (Simple): Use two nested loops. The outer loop picks characters from left to right, the inner loop finds the farthest occurrence and keeps track of the maximum.
C++
// Simple C++ program to find maximum number
// of characters between two occurrences of
// same character
#include <bits/stdc++.h>
using namespace std;
int maximumChars(string& str)
{
int n = str.length();
int res = -1;
for (int i = 0; i < n - 1; i++)
for (int j = i + 1; j < n; j++)
if (str[i] == str[j])
res = max(res, abs(j - i - 1));
return res;
}
// Driver code
int main()
{
string str = "abba";
cout << maximumChars(str);
return 0;
}
// Simple Java program to find maximum
// number of characters between two
// occurrences of same character
class GFG {
static int maximumChars(String str)
{
int n = str.length();
int res = -1;
for (int i = 0; i < n - 1; i++)
for (int j = i + 1; j < n; j++)
if (str.charAt(i) == str.charAt(j))
res = Math.max(res,
Math.abs(j - i - 1));
return res;
}
// Driver code
public static void main(String[] args)
{
String str = "abba";
System.out.println(maximumChars(str));
}
}
// This code is contributed by vt_m.
# Simple Python3 program to find maximum number
# of characters between two occurrences of
# same character
def maximumChars(str):
n = len(str)
res = -1
for i in range(0, n - 1):
for j in range(i + 1, n):
if (str[i] == str[j]):
res = max(res, abs(j - i - 1))
return res
# Driver code
if __name__ == '__main__':
str = "abba"
print(maximumChars(str))
# This code is contributed by PrinciRaj1992
// Simple C# program to find maximum
// number of characters between two
// occurrences of same character
using System;
public class GFG {
static int maximumChars(string str)
{
int n = str.Length;
int res = -1;
for (int i = 0; i < n - 1; i++)
for (int j = i + 1; j < n; j++)
if (str[i] == str[j])
res = Math.Max(res,
Math.Abs(j - i - 1));
return res;
}
// Driver code
static public void Main ()
{
string str = "abba";
Console.WriteLine(maximumChars(str));
}
}
// This code is contributed by vt_m.
<script>
// Simple Javascript program to find maximum
// number of characters between two
// occurrences of same character
function maximumChars(str)
{
let n = str.length;
let res = -1;
for (let i = 0; i < n - 1; i++)
for (let j = i + 1; j < n; j++)
if (str[i] == str[j])
res = Math.max(res,
Math.abs(j - i - 1));
return res;
}
// Driver code
let str = "abba";
document.write(maximumChars(str));
// This code is contributed by unknown2108
</script>
Output:
2
Time Complexity : O(n^2)
Auxiliary Space: O(1), since no extra space has been taken.
Approach 2 (Efficient) : Initialize an array"FIRST" of length 26 in which we have to store the first occurrence of an alphabet in the string and another array "LAST" of length 26 in which we will store the last occurrence of the alphabet in the string. Here, index 0 corresponds to alphabet a, 1 for b and so on . After that, we will take the difference between the last and first arrays to find the max difference if they are not at the same position.
C++
// Efficient C++ program to find maximum number
// of characters between two occurrences of
// same character
#include <bits/stdc++.h>
using namespace std;
const int MAX_CHAR = 256;
int maximumChars(string& str)
{
int n = str.length();
int res = -1;
// Initialize all indexes as -1.
int firstInd[MAX_CHAR];
for (int i = 0; i < MAX_CHAR; i++)
firstInd[i] = -1;
for (int i = 0; i < n; i++) {
int first_ind = firstInd[str[i]];
// If this is first occurrence
if (first_ind == -1)
firstInd[str[i]] = i;
// Else find distance from previous
// occurrence and update result (if
// required).
else
res = max(res, abs(i - first_ind - 1));
}
return res;
}
// Driver code
int main()
{
string str = "abba";
cout << maximumChars(str);
return 0;
}
// Efficient java program to find maximum
// number of characters between two
// occurrences of same character
import java.io.*;
public class GFG {
static int MAX_CHAR = 256;
static int maximumChars(String str)
{
int n = str.length();
int res = -1;
// Initialize all indexes as -1.
int []firstInd = new int[MAX_CHAR];
for (int i = 0; i < MAX_CHAR; i++)
firstInd[i] = -1;
for (int i = 0; i < n; i++)
{
int first_ind = firstInd[str.charAt(i)];
// If this is first occurrence
if (first_ind == -1)
firstInd[str.charAt(i)] = i;
// Else find distance from previous
// occurrence and update result (if
// required).
else
res = Math.max(res, Math.abs(i
- first_ind - 1));
}
return res;
}
// Driver code
static public void main (String[] args)
{
String str = "abba";
System.out.println(maximumChars(str));
}
}
// This code is contributed by vt_m.
# Efficient Python3 program to find maximum
# number of characters between two occurrences
# of same character
MAX_CHAR = 256
def maximumChars(str1):
n = len(str1)
res = -1
# Initialize all indexes as -1.
firstInd = [-1 for i in range(MAX_CHAR)]
for i in range(n):
first_ind = firstInd[ord(str1[i])]
# If this is first occurrence
if (first_ind == -1):
firstInd[ord(str1[i])] = i
# Else find distance from previous
# occurrence and update result (if
# required).
else:
res = max(res, abs(i - first_ind - 1))
return res
# Driver code
str1 = "abba"
print(maximumChars(str1))
# This code is contributed by Mohit kumar 29
// Efficient C# program to find maximum
// number of characters between two
// occurrences of same character
using System;
public class GFG {
static int MAX_CHAR = 256;
static int maximumChars(string str)
{
int n = str.Length;
int res = -1;
// Initialize all indexes as -1.
int []firstInd = new int[MAX_CHAR];
for (int i = 0; i < MAX_CHAR; i++)
firstInd[i] = -1;
for (int i = 0; i < n; i++)
{
int first_ind = firstInd[str[i]];
// If this is first occurrence
if (first_ind == -1)
firstInd[str[i]] = i;
// Else find distance from previous
// occurrence and update result (if
// required).
else
res = Math.Max(res, Math.Abs(i
- first_ind - 1));
}
return res;
}
// Driver code
static public void Main ()
{
string str = "abba";
Console.WriteLine(maximumChars(str));
}
}
// This code is contributed by vt_m.
<script>
// Efficient javascript program to find maximum
// number of characters between two
// occurrences of same character
let MAX_CHAR = 256;
function maximumChars(str)
{
let n = str.length;
let res = -1;
// Initialize all indexes as -1.
let firstInd = new Array(MAX_CHAR);
for (let i = 0; i < MAX_CHAR; i++)
firstInd[i] = -1;
for (let i = 0; i < n; i++)
{
let first_ind = firstInd[str[i].charCodeAt(0)];
// If this is first occurrence
if (first_ind == -1)
firstInd[str[i].charCodeAt(0)] = i;
// Else find distance from previous
// occurrence and update result (if
// required).
else
res = Math.max(res, Math.abs(i
- first_ind - 1));
}
return res;
}
// Driver code
let str = "abba";
document.write(maximumChars(str));
// This code is contributed by patel2127
</script>
Output:
2
Time Complexity : O(n)
Auxiliary Space: O(256) since 256 extra space has been taken.
Similar Reads
Sum of minimum and the maximum difference between two given Strings Given two strings S1 and S2 of the same length. The task is to find the sum of the minimum and the maximum difference between two given strings if you are allowed to replace the character '+' in the strings with any other character.Note: If two strings have the same characters at every index, then t
8 min read
String with maximum number of unique characters Given an array of strings, the task is to print the string with the maximum number of unique characters.Note: Strings consists of lowercase characters.If multiple strings exists, then print any one of them.Examples: Input: arr[] = ["abc", "geeksforgeeks", "gfg", "code"]Output: "geeksforgeeks" Explan
5 min read
Longest substring with atmost K characters from the given set of characters Given a string S, an integer K and set of characters Q[], the task is to find the longest substring in string S which contains atmost K characters from the given character set Q[].Examples: Input: S = "normal", Q = {"a", "o", "n", "m", "r", "l"}, K = 1 Output: 1Explanation: All the characters in the
9 min read
Replace minimal number of characters to make all characters pair wise distinct Given a string consisting of only lowercase English alphabets. The task is to find and replace the minimal number of characters with any lower case character in the given string such that all pairs of characters formed from the string are distinct. If it is impossible to do so, print "IMPOSSIBLE". N
10 min read
Minimum characters that are to be inserted such that no three consecutive characters are same Given a string str and the task is to modify the string such that no three consecutive characters are the same. In a single operation, any character can be inserted at any position in the string. Find the minimum number of such operations required. Examples: Input : str = "aabbbcc" Output: 1 Explana
5 min read