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.
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| 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
|
Constraints:
- 1 <= nums.length <= 104
- -10^4 < nums[i], target < 10^4
- All the integers in nums are unique.
- nums is sorted in ascending order.
Solution#
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| class Solution {
public int search(int[] nums, int target) {
int lo = 0;
int hi = nums.length - 1;
while (lo < hi) {
int mid = lo + (hi - lo) / 2;
if (target <= nums[mid]) {
hi = mid;
} else {
lo = mid + 1;
}
}
return nums[lo] == target? lo: -1;
}
// symmetric, target exists in nums
public int search2(int[] nums, int target) {
int lo = 0;
int hi = nums.length - 1;
while (lo <= hi) {
int mid = lo + (hi - lo) / 2;
if (target == nums[mid]) {
return mid;
} else if (target < nums[mid]) {
hi = mid - 1;
} else {
lo = mid + 1;
}
}
return -1;
}
}
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