Find Most Frequent Vowel and Consonant - Problem

You are given a string s consisting of lowercase English letters ('a' to 'z'). Your task is to:

Find the vowel (one of 'a', 'e', 'i', 'o', or 'u') with the maximum frequency.
Find the consonant (all other letters excluding vowels) with the maximum frequency.
Return the sum of the two frequencies.

Note: If multiple vowels or consonants have the same maximum frequency, you may choose any one of them. If there are no vowels or no consonants in the string, consider their frequency as 0.

The frequency of a letter x is the number of times it occurs in the string.

Input & Output

Example 1 — Mixed Vowels and Consonants

$ Input: s = "hello"

› Output: 3

💡 Note: Vowel frequencies: e=1, o=1. Consonant frequencies: h=1, l=2. Max vowel freq = 1, max consonant freq = 2. Result: 1 + 2 = 3

Example 2 — Repeated Vowel

$ Input: s = "aabbcc"

› Output: 4

💡 Note: Vowel frequencies: a=2. Consonant frequencies: b=2, c=2. Max vowel freq = 2, max consonant freq = 2. Result: 2 + 2 = 4

Example 3 — Only Vowels

$ Input: s = "aeiou"

› Output: 1

💡 Note: All characters are vowels with frequency 1 each. No consonants. Max vowel freq = 1, max consonant freq = 0. Result: 1 + 0 = 1

Constraints

1 ≤ s.length ≤ 1000
s consists only of lowercase English letters

Visualization

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Asked in

G Google 35 a Amazon 28 M Microsoft 22 f Facebook 18

The key insight is to separate vowels and consonants while counting frequencies. Track maximum frequencies for each category and return their sum. Best approach uses single pass frequency counting with simultaneous maximum tracking. Time: O(n), Space: O(1).

Common Approaches

✓ Brute Force - Count Each Letter

⏱️ Time: O(n²) Space: O(1)

For each unique letter in the string, count its occurrences by scanning the entire string. Keep track of maximum vowel and consonant frequencies separately.

Frequency Count with Hash Map

⏱️ Time: O(n) Space: O(1)

Use a hash map to count frequency of each character in one pass through the string. Then iterate through the frequency map to find maximum frequencies for vowels and consonants separately.

Single Pass Optimized

⏱️ Time: O(n) Space: O(1)

Instead of building a complete frequency map and then finding maximums, track the maximum vowel and consonant frequencies during the counting process itself. This eliminates the need for a second pass.

Brute Force - Count Each Letter — Algorithm Steps

Step 1: For each unique letter, count its frequency by scanning entire string
Step 2: Check if letter is vowel or consonant and update respective maximum
Step 3: Return sum of maximum vowel and consonant frequencies

Visualization

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Step-by-Step Walkthrough

Find Unique Letters

Identify all unique characters in the string

Count Each Letter

For each unique letter, scan entire string to count occurrences

Track Maximums

Keep track of maximum vowel and consonant frequencies

Code -

solution.c — C

#include <stdio.h>
#include <string.h>
#include <stdbool.h>

bool isVowel(char c) {
    return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
}

int solution(char* s) {
    int len = strlen(s);
    int maxVowelFreq = 0;
    int maxConsonantFreq = 0;
    bool seen[26] = {false};
    
    // Process each unique character
    for (int i = 0; i < len; i++) {
        char ch = s[i];
        if (seen[ch - 'a']) continue;
        seen[ch - 'a'] = true;
        
        // Count frequency of this character
        int freq = 0;
        for (int j = 0; j < len; j++) {
            if (s[j] == ch) {
                freq++;
            }
        }
        
        if (isVowel(ch)) {
            if (freq > maxVowelFreq) {
                maxVowelFreq = freq;
            }
        } else {
            if (freq > maxConsonantFreq) {
                maxConsonantFreq = freq;
            }
        }
    }
    
    return maxVowelFreq + maxConsonantFreq;
}

int main() {
    char s[1001];
    fgets(s, sizeof(s), stdin);
    s[strcspn(s, "\n")] = 0;
    int result = solution(s);
    printf("%d\n", result);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n²)

For each of up to 26 unique letters, we scan the entire string of length n

✓ Linear Growth

Space Complexity

O(1)

Only using variables to track counts and maximums

✓ Linear Space

23.4K Views

Medium Frequency

~15 min Avg. Time

856 Likes

Ln 1, Col 1

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Find Most Frequent Vowel and Consonant - Problem

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Brute Force - Count Each Letter — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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