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704.binary-search.cpp
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54 lines (49 loc) · 1.3 KB
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// Tag: Array, Binary Search
// Time: O(logN)
// Space: O(1)
// Ref: -
// Note: Standard;
// Video: https://youtu.be/oxWpJtUGG_0
// 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.
//
// 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
// -104 < nums[i], target < 104
// All the integers in nums are unique.
// nums is sorted in ascending order.
//
//
class Solution {
public:
int search(vector<int>& nums, int target) {
int start = 0;
int end = nums.size();
while (start < end) {
int mid = start + (end - start) / 2;
if (nums[mid] == target) {
return mid;
}
if (nums[mid] < target) {
start = mid + 1;
} else {
end = mid;
}
}
return -1;
}
};