chore: add daily leetcode post Counting Stars-Inter-Uni Programming Contest

Author: longsizhuo

app/docs/CommunityShare/Leetcode/Counting Stars-Inter-Uni Programming Contest.md

@@ -0,0 +1,56 @@
+---
+title: Counting Stars-Inter-Uni Programming Contest.md
+date: 22/9/2024
+tags:
+  - Contest
+  - Python
+  - Binary Search
+abbrlink: a29b0a05
+---
+
+# Description:
+
+https://interunia.unswcpmsoc.com/task/Counting%20Stars/
+
+# Thinking:
+
+- Given a set of star positions, we need to calculate the minimum number of stars required to explain these positions.
+- Meteors (i.e., moving stars) move from left to right, and from high to low (x coordinates increase, y coordinates decrease), without moving horizontally or vertically.
+- Each meteor may appear in multiple positions (because it moves), and the final cumulative image will show all the positions it has passed through.
+- The positions of fixed stars remain unchanged.
+
+Therefore, we need to maintain a list of the **last y-coordinate of the current chain**.
+1. **Sort the points**: Sort them by increasing x coordinates.
+2. **Initialization**: Create an empty list `last_y` to store the last y-coordinate of each chain.
+3. **Traverse the set of points**:
+    - For each point (x, y):
+        - Use `bisect_right` to find the first position in `last_y` that is greater than the current y.
+        - If the index is less than the length of `last_y`, it means there is an existing chain that can accommodate the current point, so we update the last y-coordinate of that chain to the current y.
+        - If the index is equal to the length of `last_y`, it means no suitable chain is found, so we need to create a new chain and add the current y to `last_y`.
+
+# Code:
+
+```python
+import bisect
+
+n = int(input())
+stars = []
+
+for _ in range(n):
+    x, y = map(int, input().split())
+    stars.append((x, y))
+
+# 按 x 坐标递增排序
+stars.sort(key=lambda x: (x[0],))
+
+last_y = []
+
+for x, y in stars:
+    idx = bisect.bisect_right(last_y, y)
+    if idx < len(last_y):
+        last_y[idx] = y  # 更新链的最后一个 y 坐标
+    else:
+        last_y.append(y)  # 创建新的链
+
+print(len(last_y))
+```