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Leetcode 2278. Percentage of Letter in String

Problem Statement

Given a string s and a character letter, return the percentage of characters in the string s that equal letter rounded down to the nearest integer.

Clarifying Questions

  1. Input Constraints:
    • What is the length of the string s? (Typically, for LeetCode problems, inputs can vary, but a common constraint could be ( 1 \leq s \leq 1000 )).

    • Is the string s guaranteed to contain only lowercase/uppercase alphabetic characters, or can there be other characters?

    • Character Case Sensitivity:
    • Should the comparison between characters be case-sensitive or case-insensitive?
  2. Output Requirements:
    • How should we handle an empty string or letter not present in the string? (Considering the given problem structure, we can assume the string will not be empty.)
    • Rounding down the percentage should be done using integer division, correct?

Code

#include <string>
#include <cmath>

int percentageLetter(std::string s, char letter) {
    int count = 0;
    int length = s.length();
    
    for (char c : s) {
        if (c == letter) {
            count++;
        }
    }
    
    // Calculate the percentage and round down
    int percentage = (count * 100) / length;
    
    return percentage;
}

Strategy

  1. Initialize Counters:
    • We need a counter count to keep track of how many times letter appears in the string s.
    • Also, keep track of the length of the string using length = s.length().
  2. Count Occurrences:
    • Iterate through each character in the string:
      • If the character matches letter, increment the count.
  3. Calculate Percentage:
    • Calculate the percentage of occurrences by (count * 100) / length.
    • Since integer division in C++ automatically floors the result towards zero, this will yield the rounded-down integer percentage directly.
  4. Return Result:
    • Return the calculated percentage.

Time Complexity

This approach ensures that the function runs efficiently even for the upper limits of string length.

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