# 09.01.2025 [2185. Counting Words With a Given Prefix]

Count words with prefix #easy

09.01.2025

2185. Counting Words With a Given Prefix easy blog post substack youtube deep-dive

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Problem TLDR

Count words with prefix #easy

Intuition

Brute-force is optimal.

Approach

• how short can it be?

Complexity

• Time complexity: $$O(n)$$

• Space complexity: $$O(1)$$

Code

    fun prefixCount(words: Array<String>, pref: String) = 
        words.count { it.startsWith(pref) }

    pub fn prefix_count(words: Vec<String>, pref: String) -> i32 {
        words.iter().filter(|w| w.starts_with(&pref)).count() as _
    }

    int prefixCount(vector<string>& words, string pref) {
        int r = 0;
        for (auto &w: words) r += w.starts_with(pref);
        return r;
    }