數據結構複習(2)---線性查找,二分查找

所用數組參考上一章： 數據結構複習(1) MyArrayList—線性表

/**
	 * 線性查找 有則返回下標，否則返回-1
	 * 
	 * @param element
	 * @return
	 */
	public int search(int element) {
		for (int i = 0; i < elements.length; i++) {
			if (element == elements[i]) {
				return i;
			}
		}
		return -1;
	}

	/**
	 * 非遞歸 二分查找，有則返回下標，否則返回-1
	 * 
	 * @param element
	 * @return
	 */
	public int binarySearch(int element) {
		int begin = 0;
		int end = elements.length - 1;
		int mid = (begin + end) / 2;
		while (true) {
			if (begin > end) {
				return -1;
			}
			if (element == elements[mid]) {
				return mid;
			} else {
				if (element < elements[mid]) {
					end = mid - 1;

				} else {
					begin = mid + 1;
				}
				mid = (begin + end) / 2;
			}
		}
	}

	/**
	 * 遞歸 二分查找，有則返回下標，否則返回-1
	 * 
	 * @param element
	 * @param begin
	 * @param end
	 * @return
	 */
	public int binarySearchByRecursion(int element, int begin, int end) {
		int mid = (begin + end) / 2;
		if (begin > end) {
			return -1;
		}
		if (element < elements[mid]) {
			return binarySearchByRecursion(element, begin, mid - 1);
		} else if (element > elements[mid]) {
			return binarySearchByRecursion(element, mid + 1, end);
		} else {
			return mid;
		}
	}