题目描述
题目链接:35. Search Insert Position
Given a sorted array of distinct integers 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.
例子
例子 1
Input:
nums = [1,3,5,6], target = 5
Output:2
例子 2
Input:
nums = [1,3,5,6], target = 2
Output:1
例子 3
Input:
nums = [1,3,5,6], target = 7
Output:4
Follow Up
Note
Constraints
1 <= nums.length <= 10^4
-10^4 <= nums[i] <= 10^4
nums
contains distinct values sorted in ascending order.-10^4 <= target <= 10^4
解题思路
首先检查数组最大值是否比目标小,如果是直接返回数组长度即可。否则是二分查找进行搜索,这里注意,当二分查找找到目标时可以可以直接返回,但如果目标值存在的话,最后二分查找会停在左右两个值,右边大于目标值,左边小于目标值。这个时候目标值插入的位置应该是右侧边界,因此我们在收缩边界的时候方法是:需要收缩左边界时,让 left = mid + 1
;收缩右边界时则让 right = mid
,这样可以保证最后收缩在第一个比 target
更大的值。代码如下:
class Solution {
public:
int searchInsert(vector<int>& nums, int target) {
if (nums.size() == 0 || nums.back() < target) {
return nums.size();
}
size_t left = 0;
size_t right = nums.size() - 1;
while (left < right) {
size_t mid = (left + right) / 2;
if (nums[mid] == target) {
return mid;
} else if (nums[mid] < target) {
left = mid + 1;
} else {
right = mid;
}
}
return left;
}
};
- 时间复杂度: O(logN)
- 空间复杂度: O(1)
GitHub 代码同步地址: 35.SearchInsertPosition.cpp
其他题目: GitHub: Leetcode-C++-Solution 博客: Leetcode-Solutions