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Fix toc for the webpage of the chapter of computational complexity (#1107)
* fix the math formula in TOC * Update space_complexity.md * Update time_complexity.md * Update space_complexity.md * Update time_complexity.md --------- Co-authored-by: Yudong Jin <krahets@163.com>
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@ -717,7 +717,7 @@ $$
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![Common Types of Space Complexity](space_complexity.assets/space_complexity_common_types.png)
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### Constant Order $O(1)$
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### Constant Order $O(1)$ {data-toc-label="Constant Order"}
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Constant order is common in constants, variables, objects that are independent of the size of input data $n$.
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[file]{space_complexity}-[class]{}-[func]{constant}
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```
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### Linear Order $O(n)$
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### Linear Order $O(n)$ {data-toc-label="Linear Order"}
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Linear order is common in arrays, linked lists, stacks, queues, etc., where the number of elements is proportional to $n$:
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![Recursive Function Generating Linear Order Space Complexity](space_complexity.assets/space_complexity_recursive_linear.png)
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### Quadratic Order $O(n^2)$
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### Quadratic Order $O(n^2)$ {data-toc-label="Quadratic Order"}
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Quadratic order is common in matrices and graphs, where the number of elements is quadratic to $n$:
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![Recursive Function Generating Quadratic Order Space Complexity](space_complexity.assets/space_complexity_recursive_quadratic.png)
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### Exponential Order $O(2^n)$
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### Exponential Order $O(2^n)$ {data-toc-label="Exponential Order"}
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Exponential order is common in binary trees. Observe the below image, a "full binary tree" with $n$ levels has $2^n - 1$ nodes, occupying $O(2^n)$ space:
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![Full Binary Tree Generating Exponential Order Space Complexity](space_complexity.assets/space_complexity_exponential.png)
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### Logarithmic Order $O(\log n)$
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### Logarithmic Order $O(\log n)$ {data-toc-label="Logarithmic Order"}
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Logarithmic order is common in divide-and-conquer algorithms. For example, in merge sort, an array of length $n$ is recursively divided in half each round, forming a recursion tree of height $\log n$, using $O(\log n)$ stack frame space.
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![Common Types of Time Complexity](time_complexity.assets/time_complexity_common_types.png)
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### Constant Order $O(1)$
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### Constant Order $O(1)$ {data-toc-label="Constant Order"}
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Constant order means the number of operations is independent of the input data size $n$. In the following function, although the number of operations `size` might be large, the time complexity remains $O(1)$ as it's unrelated to $n$:
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[file]{time_complexity}-[class]{}-[func]{constant}
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```
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### Linear Order $O(n)$
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### Linear Order $O(n)$ {data-toc-label="Linear Order"}
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Linear order indicates the number of operations grows linearly with the input data size $n$. Linear order commonly appears in single-loop structures:
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It's important to note that **the input data size $n$ should be determined based on the type of input data**. For example, in the first example, $n$ represents the input data size, while in the second example, the length of the array $n$ is the data size.
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### Quadratic Order $O(n^2)$
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### Quadratic Order $O(n^2)$ {data-toc-label="Quadratic Order"}
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Quadratic order means the number of operations grows quadratically with the input data size $n$. Quadratic order typically appears in nested loops, where both the outer and inner loops have a time complexity of $O(n)$, resulting in an overall complexity of $O(n^2)$:
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[file]{time_complexity}-[class]{}-[func]{bubble_sort}
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```
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### Exponential Order $O(2^n)$
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### Exponential Order $O(2^n)$ {data-toc-label="Exponential Order"}
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Biological "cell division" is a classic example of exponential order growth: starting with one cell, it becomes two after one division, four after two divisions, and so on, resulting in $2^n$ cells after $n$ divisions.
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Exponential order growth is extremely rapid and is commonly seen in exhaustive search methods (brute force, backtracking, etc.). For large-scale problems, exponential order is unacceptable, often requiring dynamic programming or greedy algorithms as solutions.
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### Logarithmic Order $O(\log n)$
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### Logarithmic Order $O(\log n)$ {data-toc-label="Logarithmic Order"}
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In contrast to exponential order, logarithmic order reflects situations where "the size is halved each round." Given an input data size $n$, since the size is halved each round, the number of iterations is $\log_2 n$, the inverse function of $2^n$.
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This means the base $m$ can be changed without affecting the complexity. Therefore, we often omit the base $m$ and simply denote logarithmic order as $O(\log n)$.
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### Linear-Logarithmic Order $O(n \log n)$
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### Linear-Logarithmic Order $O(n \log n)$ {data-toc-label="Linear-Logarithmic Order"}
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Linear-logarithmic order often appears in nested loops, with the complexities of the two loops being $O(\log n)$ and $O(n)$ respectively. The related code is as follows:
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Mainstream sorting algorithms typically have a time complexity of $O(n \log n)$, such as quicksort, mergesort, and heapsort.
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### Factorial Order $O(n!)$
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### Factorial Order $O(n!)$ {data-toc-label="Factorial Order"}
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Factorial order corresponds to the mathematical problem of "full permutation." Given $n$ distinct elements, the total number of possible permutations is:
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@ -716,7 +716,7 @@ $$
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![常见的空间复杂度类型](space_complexity.assets/space_complexity_common_types.png)
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### 常数阶 $O(1)$
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### 常数阶 $O(1)$ {data-toc-label="常数阶"}
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常数阶常见于数量与输入数据大小 $n$ 无关的常量、变量、对象。
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[file]{space_complexity}-[class]{}-[func]{constant}
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```
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### 线性阶 $O(n)$
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### 线性阶 $O(n)$ {data-toc-label="线性阶"}
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线性阶常见于元素数量与 $n$ 成正比的数组、链表、栈、队列等:
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![递归函数产生的线性阶空间复杂度](space_complexity.assets/space_complexity_recursive_linear.png)
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### 平方阶 $O(n^2)$
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### 平方阶 $O(n^2)$ {data-toc-label="平方阶"}
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平方阶常见于矩阵和图,元素数量与 $n$ 成平方关系:
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![递归函数产生的平方阶空间复杂度](space_complexity.assets/space_complexity_recursive_quadratic.png)
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### 指数阶 $O(2^n)$
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### 指数阶 $O(2^n)$ {data-toc-label="指数阶"}
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指数阶常见于二叉树。观察下图,层数为 $n$ 的“满二叉树”的节点数量为 $2^n - 1$ ,占用 $O(2^n)$ 空间:
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![满二叉树产生的指数阶空间复杂度](space_complexity.assets/space_complexity_exponential.png)
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### 对数阶 $O(\log n)$
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### 对数阶 $O(\log n)$ {data-toc-label="对数阶"}
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对数阶常见于分治算法。例如归并排序,输入长度为 $n$ 的数组,每轮递归将数组从中点处划分为两半,形成高度为 $\log n$ 的递归树,使用 $O(\log n)$ 栈帧空间。
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![常见的时间复杂度类型](time_complexity.assets/time_complexity_common_types.png)
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### 常数阶 $O(1)$
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### 常数阶 $O(1)$ {data-toc-label="常数阶"}
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常数阶的操作数量与输入数据大小 $n$ 无关,即不随着 $n$ 的变化而变化。
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[file]{time_complexity}-[class]{}-[func]{constant}
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```
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### 线性阶 $O(n)$
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### 线性阶 $O(n)$ {data-toc-label="线性阶"}
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线性阶的操作数量相对于输入数据大小 $n$ 以线性级别增长。线性阶通常出现在单层循环中:
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值得注意的是,**输入数据大小 $n$ 需根据输入数据的类型来具体确定**。比如在第一个示例中,变量 $n$ 为输入数据大小;在第二个示例中,数组长度 $n$ 为数据大小。
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### 平方阶 $O(n^2)$
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### 平方阶 $O(n^2)$ {data-toc-label="平方阶"}
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平方阶的操作数量相对于输入数据大小 $n$ 以平方级别增长。平方阶通常出现在嵌套循环中,外层循环和内层循环的时间复杂度都为 $O(n)$ ,因此总体的时间复杂度为 $O(n^2)$ :
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[file]{time_complexity}-[class]{}-[func]{bubble_sort}
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```
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### 指数阶 $O(2^n)$
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### 指数阶 $O(2^n)$ {data-toc-label="指数阶"}
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生物学的“细胞分裂”是指数阶增长的典型例子:初始状态为 $1$ 个细胞,分裂一轮后变为 $2$ 个,分裂两轮后变为 $4$ 个,以此类推,分裂 $n$ 轮后有 $2^n$ 个细胞。
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指数阶增长非常迅速,在穷举法(暴力搜索、回溯等)中比较常见。对于数据规模较大的问题,指数阶是不可接受的,通常需要使用动态规划或贪心算法等来解决。
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### 对数阶 $O(\log n)$
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### 对数阶 $O(\log n)$ {data-toc-label="对数阶"}
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与指数阶相反,对数阶反映了“每轮缩减到一半”的情况。设输入数据大小为 $n$ ,由于每轮缩减到一半,因此循环次数是 $\log_2 n$ ,即 $2^n$ 的反函数。
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也就是说,底数 $m$ 可以在不影响复杂度的前提下转换。因此我们通常会省略底数 $m$ ,将对数阶直接记为 $O(\log n)$ 。
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### 线性对数阶 $O(n \log n)$
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### 线性对数阶 $O(n \log n)$ {data-toc-label="线性对数阶"}
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线性对数阶常出现于嵌套循环中,两层循环的时间复杂度分别为 $O(\log n)$ 和 $O(n)$ 。相关代码如下:
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主流排序算法的时间复杂度通常为 $O(n \log n)$ ,例如快速排序、归并排序、堆排序等。
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### 阶乘阶 $O(n!)$
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### 阶乘阶 $O(n!)$ {data-toc-label="阶乘阶"}
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阶乘阶对应数学上的“全排列”问题。给定 $n$ 个互不重复的元素,求其所有可能的排列方案,方案数量为:
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