Missing characters to make a string Pangram

Pangram is a sentence containing every letter in the English alphabet. Given a string, find all characters that are missing from the string, i.e., the characters that can make string a Pangram. We need to print output in alphabetic order.

Examples:

Input : welcome to geeksforgeeks
Output : abdhijnpquvxyz

Input : The quick brown fox jumps
Output : adglvyz

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

We have discussed Pangram Checking. The idea is similar, we traverse given string and mark all visited characters. At the end, we print all those characters which are not visited.

Lowercase and Uppercase character are considered same.

// C++ program to find characters that needs 
// to be added to make Pangram 
#include<bits/stdc++.h> 
using namespace std; 
const int MAX_CHAR = 26; 
  
// Returns characters that needs to be added 
// to make str 
string missingChars(string str) 
{ 
    // A boolean array to store characters 
    // present in string. 
    bool present[MAX_CHAR] = {false}; 
  
    // Traverse string and mark characters 
    // present in string. 
    for (int i=0; i<str.length(); i++) 
    { 
        if (str[i] >= 'a' && str[i] <= 'z') 
            present[str[i]-'a'] = true; 
        else if (str[i] >= 'A' && str[i] <= 'Z') 
            present[str[i]-'A'] = true; 
    } 
  
    // Store missing characters in alphabetic 
    // order. 
    string res = ""; 
    for (int i=0; i<MAX_CHAR; i++) 
        if (present[i] == false) 
            res.push_back((char)(i+'a')); 
  
    return res; 
} 
  
// Driver program 
int main() 
{ 
    string str = "The quick brown fox jumps "
                 "over the dog"; 
    cout << missingChars(str); 
    return 0; 
}         

Output:

alyz

Time Complexity : O(n)
Auxiliary Space : O(1)

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