LeetCode 35. Search Insert Position(查找插入位置)

【LeetCode 35. Search Insert Position(查找插入位置)】题目描述:

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.
You may assume no duplicates in the array.
例子:

Input: [1,3,5,6], 5 Output: 2

Input: [1,3,5,6], 2 Output: 1

Input: [1,3,5,6], 7 Output: 4

Input: [1,3,5,6], 0 Output: 0

分析:
题意:给定一个有序无重复数组,一个目标值,如果找到该值,返回对应下标;否则,返回一个下标,使得插入该值后,数组保持有序。
思路:此题采用二分法。假设数组长度的为n,我们初始化指针left = 0,right = n - 1。如果找到该值,直接返回下标;否则,最后返回指针left(因为指针left对应第一个比目标值大的数,插入该位置,可以保持有序)。
时间复杂度为O(log(n))。

代码:

#include using namespace std; class Solution { public: int searchInsert(vector& nums, int target) { int n = nums.size(); // Exceptional Case: if(n == 0){ return 0; } int left = 0, right = n - 1; while(left <= right){ int mid = (left + right) >> 1; if(nums[mid] == target){ return mid; } else if(nums[mid] < target){ left = mid + 1; } else if(nums[mid] > target){ right = mid - 1; } } return left; } };

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