From 7f109cc50580d501391f5c0693888651ea339e34 Mon Sep 17 00:00:00 2001
From: Gyunseo Lee <rbstj0311@naver.com>
Date: Wed, 10 Jul 2024 20:28:29 +0900
Subject: [PATCH]  2024-07-10 20:28:29

Affected files:
.obsidian/workspace.json
src/content/blog/leet-code-74-search-a-2d-matrix.md
---
 .obsidian/workspace.json                      | 24 +++----
 .../blog/leet-code-74-search-a-2d-matrix.md   | 63 +++++++++++++++++++
 2 files changed, 75 insertions(+), 12 deletions(-)
 create mode 100644 src/content/blog/leet-code-74-search-a-2d-matrix.md

diff --git a/.obsidian/workspace.json b/.obsidian/workspace.json
index ec5110bd1..ce119460e 100644
--- a/.obsidian/workspace.json
+++ b/.obsidian/workspace.json
@@ -13,7 +13,7 @@
             "state": {
               "type": "markdown",
               "state": {
-                "file": "src/content/blog/boj-2660-회장뽑기.md",
+                "file": "src/content/blog/leet-code-1438-longest-continuous-subarray-with-absolute-diff-less-than-or-equal-to-limit.md",
                 "mode": "source",
                 "source": false
               }
@@ -22,16 +22,16 @@
         ]
       },
       {
-        "id": "8f2f56ee0a383872",
+        "id": "c7e001a823d6f00b",
         "type": "tabs",
         "children": [
           {
-            "id": "ae733d9e70e8be2f",
+            "id": "6f0f9243e9d7c564",
             "type": "leaf",
             "state": {
               "type": "markdown",
               "state": {
-                "file": "src/content/blog/boj-6593-상범-빌딩.md",
+                "file": "src/content/blog/leet-code-74-search-a-2d-matrix.md",
                 "mode": "source",
                 "source": false
               }
@@ -103,7 +103,7 @@
             "state": {
               "type": "backlink",
               "state": {
-                "file": "src/content/blog/boj-6593-상범-빌딩.md",
+                "file": "src/content/blog/leet-code-74-search-a-2d-matrix.md",
                 "collapseAll": false,
                 "extraContext": false,
                 "sortOrder": "alphabetical",
@@ -120,7 +120,7 @@
             "state": {
               "type": "outgoing-link",
               "state": {
-                "file": "src/content/blog/boj-6593-상범-빌딩.md",
+                "file": "src/content/blog/leet-code-74-search-a-2d-matrix.md",
                 "linksCollapsed": false,
                 "unlinkedCollapsed": true
               }
@@ -143,7 +143,7 @@
             "state": {
               "type": "outline",
               "state": {
-                "file": "src/content/blog/boj-6593-상범-빌딩.md"
+                "file": "src/content/blog/leet-code-74-search-a-2d-matrix.md"
               }
             }
           }
@@ -166,18 +166,19 @@
       "table-editor-obsidian:Advanced Tables Toolbar": false
     }
   },
-  "active": "ae733d9e70e8be2f",
+  "active": "6f0f9243e9d7c564",
   "lastOpenFiles": [
+    "src/content/blog/leet-code-1438-longest-continuous-subarray-with-absolute-diff-less-than-or-equal-to-limit.md",
     "src/content/blog/boj-2660-회장뽑기.md",
+    "src/content/blog/leet-code-74-search-a-2d-matrix.md",
+    "src/content/blog/leet-code-64-minimum-path-sum.md",
     "src/content/blog/boj-6593-상범-빌딩.md",
     "src/content/blog/boj-2529-부등호.md",
     "src/content/blog/왜-node에서-pino-logger를-이용한-log-io는-cpu-usage에-큰-영향이-없을까.md",
     "src/content/blog/.md",
     "src/content/blog/boj-1309-동물원.md",
-    "src/content/blog/leet-code-1438-longest-continuous-subarray-with-absolute-diff-less-than-or-equal-to-limit.md",
     "src/content/blog/leet-code-438-find-all-anagrams-in-a-string.md",
     "src/content/blog/boj-10159-저울.md",
-    "src/content/blog/leet-code-64-minimum-path-sum.md",
     "src/content/blog/leet-code-17-letter-combinations-of-a-phone-number.md",
     "src/content/blog/boj-2841-외계인의-기타-연주.md",
     "src/content/blog/boj-1926-그림.md",
@@ -212,7 +213,6 @@
     "dist/tags/ostep/1/index.html",
     "dist/tags/ostep/1",
     "dist/posts/우테코-2차-소감문.png",
-    "src/content/blog/boj-11725-트리의-부모-찾기.md",
-    "src/content/blog/boj-1935-후위-표기식2.md"
+    "src/content/blog/boj-11725-트리의-부모-찾기.md"
   ]
 }
\ No newline at end of file
diff --git a/src/content/blog/leet-code-74-search-a-2d-matrix.md b/src/content/blog/leet-code-74-search-a-2d-matrix.md
new file mode 100644
index 000000000..c3ecd8fb8
--- /dev/null
+++ b/src/content/blog/leet-code-74-search-a-2d-matrix.md
@@ -0,0 +1,63 @@
+---
+author: Gyunseo Lee
+title: "LeetCode 74: Search a 2D Matrix"
+pubDatetime: 2024-07-10T20:02:00+09:00
+modDatetime: 2024-07-10T20:02:00+09:00
+featured: false
+draft: false
+tags:
+  - PS
+  - Algorithms
+  - Binary-Search
+  - LeetCode
+description: 이분탐색 구현은 암기하고 있도록 하자
+ogImage: ""
+---
+
+## Table of contents
+
+## 들어가며
+
+이 문제를 처음 읽었을 때, 각 행마다 bisect_left, bisect_right 쿼리를 날려서 문제를 풀려고 했습니다.  
+근데 그러면 시간 복잡도가 Order of mLgn이 되더라고요. 그러면 문제에서 요구한 Order of Lg(mn)보다 크게 돼서, 시간 초과가 납니다.  
+그래서 하는 수 없이 이분 탐색을 그냥 구현하기로 했습니다.😀
+
+## 접근
+
+matrix에 이분탐색을 어떻게 할까 생각을 해 봤습니다.  
+matrix를 행별로 끊어서 늘어 뜨리면 결국 하나의 정렬된 리스트가 될 것이라는 아이디어에서 출발했습니다.  
+그러면 list의 idx를 열개수로 나눈 몫과 나머지가 matrix의 좌표가 돼 버립니다.
+
+## 구현
+
+```python
+class Solution:
+    def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
+        r = len(matrix)
+        c = len(matrix[0])
+        def binary_search():
+            def is_valid(idx):
+                i, j = idx // c, idx % c
+                if matrix[i][j] > target:
+                    return True
+                return False
+
+            lo = -1
+            hi = r * c
+            while lo + 1 < hi:
+                mid = (lo + hi) // 2
+                if is_valid(mid):
+                    hi = mid
+                else:
+                    lo = mid
+            # lo is cross point
+            if matrix[lo // c][lo % c] == target:
+                return True
+            else:
+                return False
+        return binary_search()
+```
+
+이분탐색은 off-by-one Error가 나기 쉽습니다.  
+그래서 [이분 탐색 헷갈리지 않게 구현하기](https://www.acmicpc.net/blog/view/109)의 아티클을 예전에 읽은 적이 있습니다.  
+해당 아티클의 발상과 아이디어를 많이 기억해 나가면서 구현을 했습니다.