/*
We want to sort characters in this strict order:
1. lowercase letters (a–z)
2. uppercase letters (A–Z)
3. odd digits (1,3,5,7,9)
4. even digits (0,2,4,6,8)
Strategy:
---------
Assign each character a "category rank" and sort by:
(category rank, natural character order)
JavaScript's Array.sort() with a custom comparator
is the idiomatic and efficient way to do this.
*/
/// Returns category rank for sorting.
/// Lower rank = comes earlier.
function category(c) {
if (c >= "a" && c <= "z") return 0; // lowercase
if (c >= "A" && c <= "Z") return 1; // uppercase
if (c >= "0" && c <= "9") {
const d = c.charCodeAt(0) - "0".charCodeAt(0);
return (d % 2 === 1) ? 2 : 3; // odd digits → 2, even digits → 3
}
return 4; // fallback (should not happen for alphanumeric input)
}
/// Custom comparator for sorting characters
function compareChars(a, b) {
const ca = category(a);
const cb = category(b);
if (ca !== cb)
return ca - cb; // sort by category first
return a.localeCompare(b); // tie-breaker: natural order
}
function sortAlphaNumeric(s) {
// Convert string to array of characters
const arr = [...s];
// Sort using custom comparator
arr.sort(compareChars);
// Rebuild sorted string
return arr.join('');
}
// Usage
const s = "a2B3cD8f1Z0";
const result = sortAlphaNumeric(s);
console.log("Sorted result:", result);
/*
run:
Sorted result: acfBDZ13028
*/
