leetcode/704.binary-search.java at master · ShawnLi1014/leetcode · GitHub

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/*
 * @lc app=leetcode id=704 lang=java
 *
 * [704] Binary Search
 *
 * https://leetcode.com/problems/binary-search/description/
 *
 * algorithms
 * Easy (47.89%)
 * Likes:    275
 * Dislikes: 32
 * Total Accepted:    57.3K
 * Total Submissions: 118.8K
 * Testcase Example:  '[-1,0,3,5,9,12]\n9'
 *
 * Given a sorted (in ascending order) integer array nums of n elements and a
 * target value, write a function to search target in nums. If target exists,
 * then return its index, otherwise return -1.
 *
 *
 * Example 1:
 *
 *
 * Input: nums = [-1,0,3,5,9,12], target = 9
 * Output: 4
 * Explanation: 9 exists in nums and its index is 4
 *
 *
 *
 * Example 2:
 *
 *
 * Input: nums = [-1,0,3,5,9,12], target = 2
 * Output: -1
 * Explanation: 2 does not exist in nums so return -1
 *
 *
 *
 *
 * Note:
 *
 *
 * You may assume that all elements in nums are unique.
 * n will be in the range [1, 10000].
 * The value of each element in nums will be in the range [-9999, 9999].
 *
 *
 */
class Solution {
    public int search(int[] nums, int target) {
        int lo = 0, hi = nums.length - 1;
        int mid;
        while (lo <= hi) {
            mid = (lo + hi) / 2;
            if (nums[mid] == target) {
                return mid;
            } else {
                if (nums[mid] < target) {
                    lo = mid + 1;
                } else {
                    hi = mid - 1;
                }
            }
        }
        return -1;
    }
}
// Time complexity O(logN), space complexity O(1)