add(coding/3174): clear-digits

source/coding/3174-clear-digits.md

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+---
+title: 3174. Clear Digits
+notebook: coding
+tags:
+- easy
+date: 2025-02-10 10:07:28
+updated: 2025-02-10 10:07:28
+---
+## Problem
+
+You are given a string `s`.
+
+Your task is to remove **all** digits by doing this operation repeatedly:
+
+- Delete the _first_ digit and the **closest** **non-digit** character to its _left_.
+
+Return the resulting string after removing all digits.
+
+<https://leetcode.com/problems/clear-digits/>
+
+**Example 1:**
+
+> Input: `s = "abc"`
+> Output: `"abc"`
+> Explanation:
+> There is no digit in the string.
+
+**Example 2:**
+
+> Input: `s = "cb34"`
+> Output: `""`
+> Explanation:
+> First, we apply the operation on `s[2]`, and s becomes `"c4"`.
+> Then we apply the operation on `s[1]`, and s becomes `""`.
+
+**Constraints:**
+
+- `1 <= s.length <= 100`
+- `s` consists only of lowercase English letters and digits.
+- The input is generated such that it is possible to delete all digits.
+
+## Test Cases
+
+``` python
+class Solution:
+    def clearDigits(self, s: str) -> str:
+```
+
+{% asset_code coding/3174-clear-digits/solution_test.py %}
+
+## Thoughts
+
+用一个栈记录结果字符串的字符。
+
+遍历 s 的每一个字符，如果不是数字则压栈，如果是数字则从栈里弹出最后一个字符即可。
+
+时间复杂度 `O(n)`，附加的空间复杂度 `O(n)`。
+
+## Code
+
+{% asset_code coding/3174-clear-digits/solution.py %}

source/coding/3174-clear-digits/solution.py

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+class Solution:
+    def clearDigits(self, s: str) -> str:
+        stack: list[str] = []
+        for c in s:
+            if c.isdigit():
+                stack.pop()
+            else:
+                stack.append(c)
+
+        return ''.join(stack)

source/coding/3174-clear-digits/solution_test.py

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+import pytest
+
+from solution import Solution
+
+
+@pytest.mark.parametrize('s, expected', [
+    ("abc", "abc"),
+    ("cb34", ""),
+])
+@pytest.mark.parametrize('sol', [Solution()])
+def test_solution(sol, s, expected):
+    assert sol.clearDigits(s) == expected