Leetcode skimming ---704

subject ： Given a  n  The elements are ordered （ Ascending ） integer array  nums And a target value  target  , Write a function search  nums  Medium target, If the target value has a return subscript , Otherwise return to -1.

Input ：nums= [-1,0,3,5,9,12], target = 9

Output ：4

Method 1 ： Two points search

class Solution {
public:
    int search(vector<int>& nums, int target) {
        int low = 0, high = nums.size() - 1;
        while (low <= high) {
            int mid = (high - low) / 2 + low;
            int num = nums[mid];
            if (num == target) {
                return mid;
            } else if (num > target) {
                high = mid - 1;
            } else {
                low = mid + 1;
            }
        }
        return -1;
    }
};

Complexity analysis

Time complexity ：O(logn)

Spatial complexity ：O(1)