/**
* Finds the element with the minimum number of occurrences in an array.
*
* @template T - The type of elements in the array.
* @param array - The input array to evaluate.
* @returns The least frequent element, or `undefined` if the array is empty or invalid.
*/
export function findMinOccurrence<T>(array: readonly T[]): T | undefined {
if (!array || array.length === 0) {
return undefined;
}
// 1. Tally element frequencies O(N)
const counts: Map<T, number> = new Map<T, number>();
for (const item of array) {
const currentCount: number = counts.get(item) ?? 0;
counts.set(item, currentCount + 1);
}
// 2. Find the entry with the minimum count O(K)
let minElement: T | undefined = undefined;
let minCount: number = Infinity;
for (const [item, count] of counts.entries()) {
if (count < minCount) {
minCount = count;
minElement = item;
}
}
return minElement;
}
// Example usage:
const arr: number[] = [1, 3, 1, 1, 4, 4, 5, 5, 4, 2, 2, 2, 3, 3, 3];
const result: number | undefined = findMinOccurrence<number>(arr);
if (result !== undefined) {
console.log(result); // Output: 5
} else {
console.log("The array was empty.");
}
/*
run:
5
*/
