0704 - Binary Search

0704 - Binary Search

Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1.

You must write an algorithm with O(log n) runtime complexity.

Examples

Input: nums = [-1,0,3,5,9,12], target = 9 Output: 4 Explanation: 9 exists in nums and its index is 4

Input: nums = [-1,0,3,5,9,12], target = 2 Output: -1 Explanation: 2 does not exist in nums so return -1

Constraints

1 <= nums.length <= 104 -104 < nums[i], target < 104 All the integers in nums are unique. nums is sorted in ascending order.

Java Solution

class Solution {
    public int search(int[] nums, int target) {
        int left = 0;
        int right = nums.length-1;
        while(left <= right) {
            int mid = left + (right-left)/2;
            if(nums[mid] == target) return mid;
            if(nums[mid] < target) left = mid+1;
            else right = mid - 1;
        }
        return -1;
    }
}