From f2429990889ee46072f250e3bd6e178098fc474a Mon Sep 17 00:00:00 2001
From: masterMJ <okwow123@naver.com>
Date: Sun, 23 Aug 2026 13:03:17 +0900
Subject: [PATCH] Create 315. Count of Smaller Numbers After Self.py

---
 ...5. Count of Smaller Numbers After Self.py" | 62 +++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 "leetcode3/\352\271\200\353\257\274\354\240\234/315. Count of Smaller Numbers After Self.py"

diff --git "a/leetcode3/\352\271\200\353\257\274\354\240\234/315. Count of Smaller Numbers After Self.py" "b/leetcode3/\352\271\200\353\257\274\354\240\234/315. Count of Smaller Numbers After Self.py"
new file mode 100644
index 00000000..c99206b6
--- /dev/null
+++ "b/leetcode3/\352\271\200\353\257\274\354\240\234/315. Count of Smaller Numbers After Self.py"	
@@ -0,0 +1,62 @@
+from typing import List
+
+
+class Solution:
+    def countSmaller(self, nums: List[int]) -> List[int]:
+
+        n = len(nums)
+        counts = [0] * n
+
+        # (값, 원래 index)
+        arr = [(nums[i], i) for i in range(n)]
+
+        def merge_sort(left, right):
+
+            if left >= right:
+                return
+
+            mid = (left + right) // 2
+
+            merge_sort(left, mid)
+            merge_sort(mid + 1, right)
+
+            temp = []
+
+            i = left
+            j = mid + 1
+
+            # 오른쪽에서 이미 가져온 작은 원소 개수
+            right_smaller = 0
+
+            while i <= mid and j <= right:
+
+                if arr[j][0] < arr[i][0]:
+                    temp.append(arr[j])
+                    right_smaller += 1
+                    j += 1
+
+                else:
+                    # arr[i]보다 작은 오른쪽 원소들의 개수
+                    counts[arr[i][1]] += right_smaller
+
+                    temp.append(arr[i])
+                    i += 1
+
+            # 왼쪽에 남은 원소
+            while i <= mid:
+                counts[arr[i][1]] += right_smaller
+
+                temp.append(arr[i])
+                i += 1
+
+            # 오른쪽에 남은 원소
+            while j <= right:
+                temp.append(arr[j])
+                j += 1
+
+            # 정렬된 결과를 원래 배열에 반영
+            arr[left:right + 1] = temp
+
+        merge_sort(0, n - 1)
+
+        return counts