Print First Letter of Every Word in the String

Problem

Given a string S, the task is to create a string with the first letter of every word in the string.

Examples:

Example 1:

Input: 
S = "geeks for geeks"
Output: gfg

Example 2:

Input: 
S = "bad is good"
Output: big

Your task:

You don't need to read input or print anything. Your task is to complete the function firstAlphabet() which takes string S as input parameter and returns a string that contains the first letter of every word in S.

• Expected Time Complexity: $O(|S|)$
• Expected Auxiliary Space: $O(|S|)$

Constraints:

• $1<=N<=10^5$
• $0<=a[i]<=10^5$

Solution

Python

def firstAlphabet(self, S):
	words = S.split()
    result = ""
    for word in words:
        result += word[0]
    return result

Java

String firstAlphabet(String S) {
    String[] words = S.split("\\s+");
    StringBuilder result = new StringBuilder();
    for (String word : words) {
        if (!word.isEmpty()) {  
            result.append(word.charAt(0));
        }
    }
    return result.toString();
}

C++

string firstAlphabet(string S) {
    istringstream iss(S);
    string word;
    string result;
    while (iss >> word) {
        result += word[0];
    }
    return result;
}

C

char* firstAlphabet(char S[]) {
    char result[100000];  
    int result_index = 0;
    int i = 0;
    while (S[i] != '\0') {
        while (isspace(S[i])) {
            i++;
        }
        if (!isspace(S[i])) {
            result[result_index++] = S[i];
        }
        while (S[i] != '\0' && !isspace(S[i])) {
            i++;
        }
    }
    result[result_index] = '\0';
    char* final_result = (char*) malloc(strlen(result) + 1);
    strcpy(final_result, result);
    return final_result;
}

• Time Complexity: $O(|S|)$
• Auxiliary Space: $O(|S|)$