Leetcode skimming ---35

subject ： Given a sort array and a target value , Find the target value in the array , And return its index . If the target value does not exist in the array , Return to where it will be inserted in sequence . Must use a time complexity of O(log n) The algorithm of .

Input ：nums = [1,3,5,6], target = 5

Output ：2

Method 1 ： Two points search

class Solution {
public:
    int searchInsert(vector<int>& nums, int target) {
        int n = nums.size();
        int left = 0, right = n - 1, ans = n;
        while (left <= right) {
            int mid = ((right - left) >> 1) + left;
            if (target <= nums[mid]) {
                ans = mid;
                right = mid - 1;
            } else {
                left = mid + 1;
            }
        }
        return ans;
    }
};

Complexity analysis

Time complexity ：O(log n)

Spatial complexity ：O(1)