经典二分查找问题

经典二分查找问题

题目：

描述
在一个排序数组中找一个数，返回该数出现的任意位置，如果不存在，返回 -1。

样例
样例 1：
输入：nums = [1,2,2,4,5,5], target = 2
输出：1 或者 2

样例 2：
输入：nums = [1,2,2,4,5,5], target = 6
输出：-1

public class Solution {
    /**
     * @param nums: An integer array sorted in ascending order
     * @param target: An integer
     * @return: An integer
     */
    public int findPosition(int[] nums, int target) {
        // write your code here
        int len = nums.length;
        if(len == 0) {
            return -1;
        }

        int l = 0, r = len;
        while(l < r) {
            int mid = l + (r - l) / 2;
            int num = nums[mid];
            if(num == target) {
                return mid;
            } else if(num < target) {
                l = mid + 1;
            } else {
                r = mid;
            }
        }


        return -1;
    }
}

public class Solution {
    /**
     * @param nums: An integer array sorted in ascending order
     * @param target: An integer
     * @return: An integer
     */
    public int findPosition(int[] nums, int target) {
        // write your code here
        int len = nums.length;
        if(len == 0) {
            return -1;
        }

        int l = 0, r = len - 1;
        while(l <= r) {
            int mid = l + (r - l) / 2;
            if(nums[mid] == target) {
                return mid;
            } else if(nums[mid] > target) {
                r = mid - 1;
            } else {
                // System.out.println("l = " + l);
                l = mid + 1;
            }
        }

        return -1;
    }
}