识别图中算法，用 python 实现
2025-12-19
识别图中算法，用 python 实现
思考过程
**Identifying Bubble Sort**
I've zeroed in on the algorithm - it's definitely bubble sort! The "Bubble Sort Algorithm Start" node was a dead giveaway, of course. I'm now mapping out the nested loop structure, specifically how the `j` and `i` variables interact to compare and swap adjacent elements. I'm noting the conditionals within the loops to ensure I capture all aspects.
**Decoding Implementation Strategy**
I'm now formulating a plan for the Python implementation. I'm focusing on the translation of the flowchart's structure. I'm choosing to follow the loop indexing precisely as depicted in the flowchart for the most direct conversion. This will involve the use of explicit incrementing of the loop counters `i` and `j`, instead of relying on the built-in iterator of Python `for` loops with the `range()` function.
**Evaluating Code Accuracy**
I've tested both the literal and Pythonic bubble sort implementations with a range of test cases, confirming they both produce the same correct sorted output. Next, I'm verifying the algorithmic complexity to ensure efficiency. It's time to refine the summary and create the final code presentation.
这张流程图展示的是 **冒泡排序算法 (Bubble Sort)**。
### 算法逻辑解析：
1. **初始化**：获取列表长度 `len`，设置外层循环变量 `j = 1`。
2. **外层循环**：当 `j < len` 时，进入内层循环。这代表排序需要进行的轮数。
3. **内层循环**：设置内层循环变量 `i = 0`。当 `i < len - 1` 时进行两两比较。
4. **比较与交换**：
* 判断 `b[i] > b[i+1]` 是否成立。
* 如果成立（前一个数比后一个数大），则交换两个数的位置：使用临时变量 `tmp` 辅助交换。
* 如果不成立，则跳过交换。
5. **变量自增**：内层变量 `i` 加 1，外层变量 `j` 加 1，直到循环结束。
6. **输出**：输出排序后的列表。
---
### Python 代码实现：
你可以直接运行以下代码，它完全遵循流程图中的逻辑：
```python
def bubble_sort(b):
# 1. 获取列表长度
length = len(b)
# 2. 初始化外层循环变量 j = 1
j = 1
while j < length:
# 3. 初始化内层循环变量 i = 0
i = 0
while i < length - 1:
# 4. 判断 b[i] > b[i+1]
if b[i] > b[i+1]:
# 5. 进行两个数的交换 (对应流程图中的 tmp 交换逻辑)
tmp = b[i]
b[i] = b[i+1]
b[i+1] = tmp
# 6. 内层下标 i 自增
i = i + 1
# 7. 外层计数 j 自增
j = j + 1
# 8. 输出最后结果
print("排序后的结果:", b)
return b
# 测试数据
nums = [64, 34, 25, 12, 22, 11, 90]
print("原始列表:", nums)
bubble_sort(nums)
```
### 更符合 Python 习惯的写法（精简版）：
在 Python 中，我们通常使用 `for` 循环和元组解包（直接交换）来使代码更简洁：
```python
def bubble_sort_standard(b):
n = len(b)
for j in range(1, n):
for i in range(n - 1):
if b[i] > b[i+1]:
b[i], b[i+1] = b[i+1], b[i] # Python 特有的交换写法
return b
# 使用示例
nums = [5, 1, 4, 2, 8]
sorted_nums = bubble_sort_standard(nums)
print(sorted_nums)
```