Problem
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 innumsand its index is 4
Example 2:
Input:nums= [-1,0,3,5,9,12],target= 2 Output: -1 Explanation: 2 does not exist innumsso return -1
Note:
- You may assume that all elements in
numsare unique. nwill be in the range[1, 10000].- The value of each element in
numswill be in the range[-9999, 9999].
Solution: Binary Search
Time complexity: O(logn)
Space complexity: O(1)
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// Author: Huahua // Running time: 32 ms class Solution { public: int search(vector<int>& nums, int target) { int l = 0; int r = nums.size(); while (l < r) { int m = (r - l) / 2 + l; if (nums[m] == target) return m; else if (nums[m] > target) r = m; else l = m + 1; } return -1; } }; |
STL
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// Author: Huahua // Running time: 36 ms class Solution { public: int search(vector<int>& nums, int target) { auto it = lower_bound(nums.begin(), nums.end(), target); if (it == nums.end() || *it != target) return -1; return it - nums.begin(); } }; |
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