重构检查数组中是否存在项

function linearSearch(arr, target) {
    for (let i = 0; i < arr.length; i++) {
        if (arr[i] === target) {
            return true;
        }
    }
    return false;
}

function binarySearch(arr, target) {
    let left = 0;
    let right = arr.length - 1;
    while (left <= right) {
        const mid = Math.floor((left + right) / 2);
        if (arr[mid] === target) {
            return true;
        } else if (arr[mid] < target) {
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }
    return false;
}

function hashTableSearch(arr, target) {
    const set = new Set(arr);
    return set.has(target);
}