From 3e14c5317f8e56e9f310497cd80599b04b20e29c Mon Sep 17 00:00:00 2001
From: Hiro Funatsuka <hiro.funatsuka@gmail.com>
Date: Thu, 23 Apr 2026 23:38:07 +0900
Subject: [PATCH] Solve first unique character in a string

---
 README.md |  2 +-
 step1.md  | 26 ++++++++++++++++++++++++--
 step2.md  | 15 +++++++++++++++
 step3.md  | 20 +++++++++++++++++---
 4 files changed, 57 insertions(+), 6 deletions(-)

diff --git a/README.md b/README.md
index b9c1787..c4f0422 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # LeetCode
 
-## 問題: 
+## 問題: [387. First Unique Character in a String](https://leetcode.com/problems/first-unique-character-in-a-string/description/)
 
 ## 前提
 
diff --git a/step1.md b/step1.md
index 54ebbc1..99f4618 100644
--- a/step1.md
+++ b/step1.md
@@ -1,7 +1,29 @@
 # Step 1
 
+- setとdictを用意する
+- 各characterをsetに追加、初見ならdictにインデックスと一緒に追加
+- characterが再び現れたらdictから削除
+- ループが一周したら、dictでループし最小のインデックスを返す
+
 ```python
+class Solution:
+    def firstUniqChar(self, s: str) -> int:
+        chars = set()
+        unique_char_to_idx = dict()
+
+        for idx, char in enumerate(s):
+            if char in chars:
+                unique_char_to_idx.pop(char, None)
+            else:
+                chars.add(char)
+                unique_char_to_idx[char] = idx
+
+        if len(unique_char_to_idx) == 0:
+            return -1
+
+        return min(unique_char_to_idx.values())
 ```
-時間計算量:
 
-空間計算量:
+時間計算量: O(n)
+
+空間計算量: O(n)
diff --git a/step2.md b/step2.md
index 6ec3360..2d65ed9 100644
--- a/step2.md
+++ b/step2.md
@@ -1,4 +1,19 @@
 # Step 2
 
+- hashを2つ宣言する必要なかった
+
 ```python
+class Solution:
+    def firstUniqChar(self, s: str) -> int:
+        character_to_idx = dict()
+        n = len(s)
+
+        for idx, character in enumerate(s):
+            if character in character_to_idx:
+                character_to_idx[character] = n
+            else:
+                character_to_idx[character] = idx
+
+        res = min(character_to_idx.values())
+        return -1 if res == n else res
 ```
diff --git a/step3.md b/step3.md
index 522daa6..edd4eee 100644
--- a/step3.md
+++ b/step3.md
@@ -1,9 +1,23 @@
 # Step 3
 
 ```python
+class Solution:
+    def firstUniqChar(self, s: str) -> int:
+        character_to_idx = dict()
+        n = len(s)
+
+        for idx, character in enumerate(s):
+            if character in character_to_idx:
+                character_to_idx[character] = n
+            else:
+                character_to_idx[character] = idx
+
+        res = min(character_to_idx.values())
+        return -1 if res == n else res
 ```
-1回目: 分　秒
 
-2回目: 分　秒
+1回目: 1分　53秒
+
+2回目: 1分　54秒
 
-3回目: 分　秒
+3回目: 1分　45秒