对字符串进行最小更改以使所有子字符串不同

给定一个字符串，找出对它的最小更改次数，以使该字符串的所有子字符串变得不同。
例子：

Input :  str = "aab"
Output : 1
If we change one instance of 'a'
to any character from 'c' to 'z',
we get all distinct substrings.

Input : str = "aa"
Output : 1

为了使所有子字符串不同，每个字符都必须不同。所以我们只需要计算重复字符的数量。如果字符串的长度大于 26，那么我们不能将其转换为具有所有不同子字符串的字符串（这里我们假设字符串应该只包含小写字符，'a' 到 'z'）

C++

// CPP program to count number of changes
// to make all substrings distinct.
#include 
using namespace std;
 
const int MAX_CHAR = 26;
 
// Returns minimum changes to str so
// that no substring is repeated.
int minChanges(string &str)
{
    int n = str.length();
 
    // If length is more than maximum
    // allowed characters, we cannot
    // get the required string.
    if (n > MAX_CHAR)
       return -1;
 
    // Variable to store count of
    // distinct characters
    int dist_count = 0;
     
    // To store counts of different
    // characters
    int count[MAX_CHAR] = {0};
 
    for (int i = 0; i < n; i++) {
        if (count[str[i] - 'a'] == 0)
            dist_count++;
        count[(str[i] - 'a')]++;
    }
 
    // Answer is, n - number of distinct char
    return (n - dist_count);
}
 
// Driver function
int main()
{
    string str = "aebaecedabbee";
    cout << minChanges(str);
    return 0;
}

Java

// JAVA program to count number of changes
// to make all substrings distinct.
import java.lang.*;
import java.util.*;
 
class GFG
{
    static final int MAX_CHAR = 26;
     
    // Returns minimum changes to str so
    // that no substring is repeated.
    public static int minChanges(String str)
    {
         
        int n = str.length();
         
        // If length is more than maximum
        // allowed characters, we cannot
        // get the required string.
        if (n > MAX_CHAR)
            return -1;
         
        // Variable to store count of
        // distinct characters
        int dist_count = 0;
        int count[] = new int[MAX_CHAR];
         
        // To store counts of different
        // characters
        for(int i = 0; i < MAX_CHAR; i++)
            count[i] = 0;
         
        for (int i = 0; i < n; i++)
        {
            if(count[str.charAt(i)-'a'] == 0)
                dist_count++;
            count[str.charAt(i)-'a']++;
        }
         
        // Answer is, n - number of distinct char
        return (n-dist_count);
    }
     
    //Driver function
    public static void main (String[] args) {
         
        String str = "aebaecedabbee";
         
        System.out.println(minChanges(str));
    }
}
 
/* This code is contributed by Akash Singh*/

Python3

# Python3 program to count number of changes
# to make all substrings distinct.
 
MAX_CHAR = [26]
 
# Returns minimum changes to str so
# that no substring is repeated.
def minChanges(str):
 
    n = len(str )
 
    # If length is more than maximum
    # allowed characters, we cannot
    # get the required string.
    if (n > MAX_CHAR[0]):
        return -1
 
    # Variable to store count of
    # distinct characters
    dist_count = 0
     
    # To store counts of different
    # characters
    count = [0] * MAX_CHAR[0]
 
    for i in range(n):
        if (count[ord(str[i]) - ord('a')] == 0) :
            dist_count += 1
        count[(ord(str[i]) - ord('a'))] += 1
     
    # Answer is, n - number of distinct char
    return (n - dist_count)
 
# Driver Code
if __name__ == '__main__':
    str = "aebaecedabbee"
    print(minChanges(str))
         
# This code is contributed
# by SHUBHAMSINGH10

C#

// C# program to count number of changes
// to make all substrings distinct.
using System;
 
class GFG
{
    static int MAX_CHAR = 26;
     
    // Returns minimum changes to str so
    // that no substring is repeated.
    public static int minChanges(string str)
    {
         
        int n = str.Length;
         
        // If length is more than maximum
        // allowed characters, we cannot
        // get the required string.
        if (n > MAX_CHAR)
            return -1;
         
        // Variable to store count of
        // distinct characters
        int dist_count = 0;
        int []count = new int[MAX_CHAR];
         
        // To store counts of different
        // characters
        for(int i = 0; i < MAX_CHAR; i++)
            count[i] = 0;
         
        for (int i = 0; i < n; i++)
        {
            if(count[str[i] - 'a'] == 0)
                dist_count++;
            count[str[i] - 'a']++;
        }
         
        // Answer is, n - number of distinct char
        return (n - dist_count);
    }
     
    //Driver function
    public static void Main () {
         
        string str = "aebaecedabbee";
         
        Console.WriteLine(minChanges(str));
    }
}
 
/* This code is contributed by Akash Singh*/

PHP

 26)
    return -1;
 
    // Variable to store count of
    // distinct characters
    $dist_count = 0;
     
    // To store counts of different
    // characters
    $count = array_fill(0, 26, 0);
    for ($i = 0; $i < $n; $i++)
    {
        if ($count[ord($str[$i]) - 97] == 0)
            $dist_count++;
        $count[ord($str[$i]) -97]++;
    }
 
    // Answer is, n - number of
    // distinct char
    return ($n - $dist_count);
}
 
// Driver Code
$str = "aebaecedabbee";
echo minChanges($str);
 
// This code is contributed by mits
?>

Javascript

输出：