二分查找变形

package test;

import java.util.Arrays;

public class N172 {
	public static void main(String[] args) {
		int[] a = { 1, 34, 4, 4, 5, 4, 6, 2345, 0 };
		Arrays.sort(a);
		System.out.println(Arrays.toString(a));
		System.out.println(search(0, a.length - 1, 4, a));
		System.out.println(search2(0, a.length - 1, 4, a));
	}

	/**
	 * 找到第一个大于 x 的数的下标
	 * 
	 * @param l
	 * @param r
	 * @param x
	 * @param a
	 * @return
	 */
	static int search(int l, int r, int x, int[] a) {
		while (l <= r) {
			int mid = (l + r) / 2;
			if (x < a[mid]) {
				r = mid - 1;
			} else {
				l = mid + 1;
			}
		}
		return l;
	}

	/**
	 * 找到第一个小于 x 的下标
	 * 
	 * @param l
	 * @param r
	 * @param x
	 * @param a
	 * @return
	 */
	static int search2(int l, int r, int x, int[] a) {
		while (l <= r) {
			int mid = (l + r) / 2;
			if (x <= a[mid]) {
				r = mid - 1;
			} else {
				l = mid + 1;
			}
		}
		return r;
	}
}