code.rs

/*
Given two strings, find the number of common characters between them.

Example

For s1 = "aabcc" and s2 = "adcaa", the output should be
commonCharacterCount(s1, s2) = 3.

Strings have 3 common characters - 2 "a"s and 1 "c".
*/

use std::collections::HashMap;

fn commonCharacterCount(s1: String, s2: String) -> i32 {
    let mut charCounts = (HashMap::new(), HashMap::new());

    populate_hashmap(&mut charCounts.0, &s1);
    populate_hashmap(&mut charCounts.1, &s2);
    
    let mut n = 0;
    // I am not allowed to use inclusive range syntax on codefights ;(
    for i in ('a' as u8)..('z' as u8) + 1 {
        n += i32::min(
            *charCounts.0.entry(i as char).or_insert(0),
            *charCounts.1.entry(i as char).or_insert(0)
        );
    }
    
    return n;
}

fn populate_hashmap(map: &mut HashMap<char, i32>, string: &str) {
    for c in string.chars() {
        let count = map.entry(c).or_insert(0);
        *count += 1;
    }
}