From 7a7a4e760cdd7faebbe674728a05f889eaecb331 Mon Sep 17 00:00:00 2001
From: Brave Kim <ygflove@bible.ac.kr>
Date: Wed, 29 Jun 2022 13:50:47 +0900
Subject: [PATCH 01/10] :white_check_mark: Finish 'what is sliding window'

---
 15/yongki/SlidingWindow.md | 101 +++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 15/yongki/SlidingWindow.md

diff --git a/15/yongki/SlidingWindow.md b/15/yongki/SlidingWindow.md
new file mode 100644
index 0000000..fcb616a
--- /dev/null
+++ b/15/yongki/SlidingWindow.md
@@ -0,0 +1,101 @@
+# 슬라이딩 윈도우
+
+## 이론
+
+<details>
+<br/>
+
+대표적으로 배열에서 연이은 k개의 최대합을 구하는 문제에 사용된다.
+
+Brute force의 O(kn)으로 해결하는 문제를 O(n)으로 줄일수 있다.
+
+**Brute force**
+
+```js
+function maxSum(arr, k) {
+  let max = 0;
+  const N = arr.length;
+
+  for (let i = 0; i <= N - k; i++) {
+    let sum = 0;
+    
+    for(let j = 0; j < k; j++)
+      sum = sum + arr[i + j];
+
+    max = Math.max(max, sum);
+  }  
+
+  return max;
+}
+
+(function main() {
+  assert.equal(
+    maxSum(
+      arr = [1, 4, 2, 10, 2, 3, 1, 0, 20],
+      k = 4
+    ),
+    24
+  )
+})();
+```
+
+**슬라이딩 윈도우**
+
+    arr = [1, 4, 2, 10, 2, 3, 1, 0, 20]
+    k = 4
+
+    k만큼의 요소를 arr에서 sum하면 14이다.
+
+      [1, 4, 2, 10]
+
+    k인덱스부터 루프를 돈다.
+
+      [2, 3, 1, 0, 20]
+
+    sum은 k만큼의 요소의 합을 유지한다.
+
+      [4, 2, 10, 2]를 유지하기 위해 요소1을 제거
+
+    매 루프마다 max와 sum의 max를 구한다.
+
+```js
+function maxSum(arr, k) {
+  let max = 0;
+  let sum = 0;
+
+  const N = arr.length;
+
+  for (let i = 0; i < k; i++) {
+    sum += arr[i];
+    max = sum;
+  }
+
+  for (let i = k; i < N; i++) {    
+    sum += arr[i] - arr[i - k];
+
+    max = Math.max(max, sum);
+  }
+
+  return max;
+}
+
+(function main() {
+  assert.equal(
+    maxSum(
+      arr = [1, 4, 2, 10, 2, 3, 1, 0, 20],
+      k = 4
+    ),
+    24
+  )
+})();
+```
+
+</details>
+
+## 문제 리스트
+
+<hr/>
+
+## 참고 문헌
+
+[Window Sliding Technique](https://www.geeksforgeeks.org/window-sliding-technique/) ━ *GeeksforGeeks*
\ No newline at end of file

From 24f378b8bda0cb44f5dbe6952c65f714b1a64ed3 Mon Sep 17 00:00:00 2001
From: Brave Kim <ygflove@bible.ac.kr>
Date: Wed, 29 Jun 2022 18:53:17 +0900
Subject: [PATCH 02/10] :white_check_mark: Solve 219

---
 15/yongki/SlidingWindow.md | 42 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/15/yongki/SlidingWindow.md b/15/yongki/SlidingWindow.md
index fcb616a..f671b54 100644
--- a/15/yongki/SlidingWindow.md
+++ b/15/yongki/SlidingWindow.md
@@ -94,6 +94,48 @@ function maxSum(arr, k) {
 
 ## 문제 리스트
 
+<details>
+<summary>219. Contains Duplicate II
+  <a href="https://leetcode.com/problems/contains-duplicate-ii/">👊</a>
+</summary>
+
+### 문제 회고
+
+이전 해결했던 이력이 있었다.
+
+다만 슬라이딩 윈도우를 푼것인지도 몰랐다.
+
+이론에서 다룬 형태외에도 Map을 사용한 형태도 해당됨을 알게되었다.
+
+### 문제 풀이
+
+```js
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {boolean}
+ *
+ * time:  O(n)
+ * space: O(k)
+ */
+var containsNearbyDuplicate = function (nums, k) {
+  const window = new Map();
+
+  for (const [idx, num] of nums.entries()) {
+    if (
+      window.has(num)
+      && Math.abs(idx - window.get(num)) <= k
+    )
+      return true;
+
+    window.set(num, idx);
+  }
+  return false;
+};
+```
+
+</details>
+
 <hr/>
 
 ## 참고 문헌

From 7a88ccc089bac1e37a6ca9ceb27442084b306cc2 Mon Sep 17 00:00:00 2001
From: Brave Kim <ygflove@bible.ac.kr>
Date: Thu, 30 Jun 2022 17:29:33 +0900
Subject: [PATCH 03/10] :white_check_mark: Solve 643

---
 15/yongki/SlidingWindow.md | 42 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/15/yongki/SlidingWindow.md b/15/yongki/SlidingWindow.md
index f671b54..bc53076 100644
--- a/15/yongki/SlidingWindow.md
+++ b/15/yongki/SlidingWindow.md
@@ -136,6 +136,48 @@ var containsNearbyDuplicate = function (nums, k) {
 
 </details>
 
+<details>
+<summary>643. Maximum Average Subarray I
+  <a href="https://leetcode.com/problems/maximum-average-subarray-i/submissions/">👊</a>
+</summary>
+
+### 문제 회고
+
+이론에서 다룬 형태와 같아 고민없이 풀 수 있었다.
+
+자바스크립트에서 `Math.avg`는 없는것도 알 수 있었다.
+
+### 문제 풀이
+
+```js
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number}
+ *
+ * time:  O(n)
+ * space: O(1)
+ */
+var findMaxAverage = function (nums, k) {
+  let max = 0;
+  let sum = 0;
+
+  for (let i = 0; i < k; i++) {
+    sum += nums[i];
+    max = sum / k;
+  }
+
+  for (let i = k; i < nums.length; i++) {
+    sum += nums[i] - nums[i - k];
+    max = Math.max(max, (sum / k));
+  }
+
+  return max;
+};
+```
+
+</details>
+
 <hr/>
 
 ## 참고 문헌

From 17f2a055c30f43d16a50d6e4ea4b026dd6b74dcd Mon Sep 17 00:00:00 2001
From: Brave Kim <ygflove@bible.ac.kr>
Date: Fri, 1 Jul 2022 17:17:12 +0900
Subject: [PATCH 04/10] :white_check_mark: Solve 2269

---
 15/yongki/SlidingWindow.md | 46 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/15/yongki/SlidingWindow.md b/15/yongki/SlidingWindow.md
index bc53076..265bf41 100644
--- a/15/yongki/SlidingWindow.md
+++ b/15/yongki/SlidingWindow.md
@@ -178,6 +178,52 @@ var findMaxAverage = function (nums, k) {
 
 </details>
 
+<details>
+<summary>2269. Find the K-Beauty of a Number
+  <a href="https://leetcode.com/problems/find-the-k-beauty-of-a-number/">👊</a>
+</summary>
+
+### 문제 풀이
+
+```js
+/**
+ * @param {number} num
+ * @param {number} k
+ * @return {number}
+ *
+ * time:  O(n)
+ * space: O(n)
+ */
+var divisorSubstrings = function (num, k) {
+  const letterList = num.toString().split('');
+
+  let cur = '';
+  let cnt = 0;
+
+  for (let i = 0; i < k; i++)
+    cur += letterList[i];
+
+  if (isZeroDivisor(num, parseInt(cur)))
+    cnt += 1;
+
+  for (let i = k; i < letterList.length; i++) {
+    cur = cur.substring(1);
+    cur += letterList[i];
+
+    if (isZeroDivisor(num, parseInt(cur)))
+      cnt += 1;
+  }
+
+  return cnt;
+};
+
+var isZeroDivisor = function (num, target) {
+  return (num % target) === 0;
+};
+```
+
+</details>
+
 <hr/>
 
 ## 참고 문헌

From 545c882bdc441a9dfacedf4625ccacb76a661406 Mon Sep 17 00:00:00 2001
From: Brave Kim <ygflove@bible.ac.kr>
Date: Mon, 4 Jul 2022 19:10:46 +0900
Subject: [PATCH 05/10] :test_tube: Fail testcase at 1763

---
 15/yongki/SlidingWindow.md | 77 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)

diff --git a/15/yongki/SlidingWindow.md b/15/yongki/SlidingWindow.md
index 265bf41..8e7d47f 100644
--- a/15/yongki/SlidingWindow.md
+++ b/15/yongki/SlidingWindow.md
@@ -224,6 +224,83 @@ var isZeroDivisor = function (num, target) {
 
 </details>
 
+<details>
+<summary>1763. Longest Nice Substring
+  <a href="https://leetcode.com/problems/longest-nice-substring/">👊</a>
+</summary>
+
+### 문제 회고
+
+가변적인 결과값이 예상되어 `슬라이딩 윈도우`보단 `투 포인터` 알고리즘이 필요하다고 판단하였다.
+
+현재 동일한 알파벳의 niceSubstring은 완성하지만
+
+    Input:   "dDzeE"
+    Output:  "dD"
+
+여러 알파벳의 niceSubstring은 찾지 못했다.
+
+    Input:    "cChH"
+    Output:   "cC"
+    Expected: "cChH"
+
+### 문제 풀이
+
+```js
+/**
+ * @param {string} s
+ * @return {string}
+ *
+ * time:  O(n²)
+ * space: O(n)
+ */
+var longestNiceSubstring = function (s) {
+  var getLongestSubstring = function (...args) {
+    return args.reduce((a, b) => {
+      return (a.length === b.length) ? a
+        : (a.length > b.length) ? a
+          : b;
+    });
+  }
+
+  var getNiceSubstring = function (left, right) {
+    let cur = '';
+
+    while (
+      left >= 0
+      && right < N
+      && s[left].toLowerCase() === s[right].toLowerCase()
+    ) {
+      cur = s.substring(left, right + 1);
+      right += 1;
+    }
+
+    return cur;
+  }
+
+  /// +++ start  
+  const N = s.length;
+  let result = '';
+
+  if (N < 2)
+    return result;
+
+  for (let i = 0; i < N; i++) {
+    const niceSubstring = getNiceSubstring(i, i);
+
+    if (niceSubstring.length === 1)
+      continue;
+
+    result = getLongestSubstring(result, niceSubstring);
+    console.log(result);
+  }
+
+  return result;
+};
+```
+
+</details>
+
 <hr/>
 
 ## 참고 문헌

From 5654e9efa058e4f2f2c150c22da63ad796814b71 Mon Sep 17 00:00:00 2001
From: Brave Kim <ygflove@bible.ac.kr>
Date: Tue, 5 Jul 2022 17:15:05 +0900
Subject: [PATCH 06/10] :white_check_mark: Solve 1876

---
 15/yongki/SlidingWindow.md | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/15/yongki/SlidingWindow.md b/15/yongki/SlidingWindow.md
index 8e7d47f..e1fda41 100644
--- a/15/yongki/SlidingWindow.md
+++ b/15/yongki/SlidingWindow.md
@@ -299,6 +299,43 @@ var longestNiceSubstring = function (s) {
 };
 ```
 
+</details>
+
+<details>
+<summary>1876. Substrings of Size Three with Distinct Characters
+  <a href="https://leetcode.com/problems/substrings-of-size-three-with-distinct-characters/">👊</a>
+</summary>
+
+### 문제 풀이
+
+```js
+/**
+ * @param {string} s
+ * @return {number}
+ *
+ * time:  O(n)
+ * space: O(1)
+ */
+var countGoodSubstrings = function (s) {
+  var isGoodSubstrings = function (s) {
+    return s === [...new Set(s.split(''))].join('');
+  }
+
+  // +++ Start
+  const L = 3;
+  let result = 0;
+
+  for (let i = 0; i < s.length; i++) {
+    const substring = s.substring(i, i + L);
+
+    if (substring.length === L && isGoodSubstrings(substring))
+      result += 1;
+  }
+  return result;
+};
+```
+
+
 </details>
 
 <hr/>

From e153fab48d983b700c17237d454411b874e7b470 Mon Sep 17 00:00:00 2001
From: Brave Kim <ygflove@bible.ac.kr>
Date: Wed, 6 Jul 2022 17:30:03 +0900
Subject: [PATCH 07/10] :white_check_mark: Solve 1984

---
 15/yongki/SlidingWindow.md | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/15/yongki/SlidingWindow.md b/15/yongki/SlidingWindow.md
index e1fda41..699dfde 100644
--- a/15/yongki/SlidingWindow.md
+++ b/15/yongki/SlidingWindow.md
@@ -334,7 +334,41 @@ var countGoodSubstrings = function (s) {
   return result;
 };
 ```
+</details>
+
+<details>
+<summary>1984. Minimum Difference Between Highest and Lowest of K Scores
+  <a href="https://leetcode.com/problems/minimum-difference-between-highest-and-lowest-of-k-scores/">👊</a>
+</summary>
+
+### 문제 풀이
+
+```js
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number}
+ *
+ * time:  O(n)
+ * space: O(1)
+ */
+var minimumDifference = function (nums, k) {
+  nums.sort((a, b) => a - b);
+
+  const kIdx = k - 1;
 
+  let highScore = nums[kIdx];
+  let lowScore = nums[0];
+  let min = highScore - lowScore;  
+
+  for (let i = kIdx; i < nums.length; i++) {
+    const diffScore = nums[i] - nums[i - kIdx];
+    min = Math.min(min, diffScore);
+  }
+
+  return min;
+};
+```
 
 </details>
 

From 4cc978527ebdab3b10bf70828a8d74db2dcb382f Mon Sep 17 00:00:00 2001
From: Brave Kim <ygflove@bible.ac.kr>
Date: Thu, 7 Jul 2022 16:22:24 +0900
Subject: [PATCH 08/10] =?UTF-8?q?:test=5Ftube:=20Fail=20testcase=20at=20?=
 =?UTF-8?q?=EB=B3=B4=EC=84=9D=20=EC=87=BC=ED=95=91?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 15/yongki/SlidingWindow.md | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/15/yongki/SlidingWindow.md b/15/yongki/SlidingWindow.md
index 699dfde..7e18930 100644
--- a/15/yongki/SlidingWindow.md
+++ b/15/yongki/SlidingWindow.md
@@ -372,6 +372,42 @@ var minimumDifference = function (nums, k) {
 
 </details>
 
+<details>
+<summary>보석 쇼핑
+  <a href="https://school.programmers.co.kr/learn/courses/30/lessons/67258">👊</a>
+</summary>
+
+### 문제 회고
+
+제시된 예제는 패스했지만, 제출시 테스트케이스는 해결하지 못했다.
+
+### 문제 풀이
+
+```js
+/*
+* time:     O(n)
+* space:    O(n)
+*/
+function solution(gems) {
+  const gemTypeLength = new Set([...gems]).size;
+  const window = new Map();
+
+  for (const [idx, gem] of gems.entries()) {
+    window.set(gem, idx + 1);
+
+    if (gemTypeLength === [...window.values()].length)
+      break;
+  }
+
+  return [
+    Math.min(...window.values()),
+    Math.max(...window.values())
+  ];
+}
+```
+
+</details>
+
 <hr/>
 
 ## 참고 문헌

From 94bf6ee1442760706a63880c23ab564292b5ebc1 Mon Sep 17 00:00:00 2001
From: Brave Kim <ygflove@bible.ac.kr>
Date: Thu, 7 Jul 2022 20:24:19 +0900
Subject: [PATCH 09/10] =?UTF-8?q?:white=5Fcheck=5Fmark:=20Solve=20?=
 =?UTF-8?q?=EB=B3=B4=EC=84=9D=20=EC=87=BC=ED=95=91?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 15/yongki/SlidingWindow.md | 91 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 87 insertions(+), 4 deletions(-)

diff --git a/15/yongki/SlidingWindow.md b/15/yongki/SlidingWindow.md
index 7e18930..9368d66 100644
--- a/15/yongki/SlidingWindow.md
+++ b/15/yongki/SlidingWindow.md
@@ -379,9 +379,7 @@ var minimumDifference = function (nums, k) {
 
 ### 문제 회고
 
-제시된 예제는 패스했지만, 제출시 테스트케이스는 해결하지 못했다.
-
-### 문제 풀이
+처음 접근은 다음과 같다.
 
 ```js
 /*
@@ -406,10 +404,95 @@ function solution(gems) {
 }
 ```
 
+해당 테스트케이스는 해결하지 못했다.
+
+    ["A","B","B","B","B","B","B","C","B","A"] [8,10]
+
+    Output:   [1, 8]
+    Expected: [8, 10]
+
+### 문제 풀이
+
+문제 풀이자는 범위를 모두 기억해둔 뒤, 적은 범위 순대로 정렬을 해두었다.
+
+    // +++ map by for loop
+    Map(1) { 'A' => 0 }
+    Map(2) { 'A' => 0, 'B' => 1 }
+    Map(2) { 'A' => 0, 'B' => 2 }
+    Map(2) { 'A' => 0, 'B' => 3 }
+    Map(2) { 'A' => 0, 'B' => 4 }
+    Map(2) { 'A' => 0, 'B' => 5 }
+    Map(2) { 'A' => 0, 'B' => 6 }
+    Map(3) { 'A' => 0, 'B' => 6, 'C' => 7 }
+    Map(3) { 'A' => 0, 'C' => 7, 'B' => 8 }
+    Map(3) { 'C' => 7, 'B' => 8, 'A' => 9 }
+    
+    // +++ ranges
+    [ 
+      { start: 1, end: 8 }, 
+      { start: 1, end: 9 }, 
+      { start: 8, end: 10 } 
+    ]
+
+    // +++ sort by compact ranges
+    [ 
+      { start: 8, end: 10 }   // +++ result!
+      { start: 1, end: 8 }, 
+      { start: 1, end: 9 }, 
+    ]
+
+인상적인 것은 map의 values의 순서를 오름차순으로 맞추도록 key를 갱신하는 작업이 있었다는 것이다.
+
+이는 범위를 추가할때, 어디가 start인지 end인지를 찾는 작업을 없애주었다.
+
+또한, 범위의 start를 찾을 때 다음과 같은 방법외에
+
+    start: [...gemMap.values()][0] + 1,
+
+이터레이터를 활용했다는 점이 인상깊었다.
+
+    start: gemMap.values().next().value + 1,
+
+```js
+/*
+* time:     O(n)
+* space:    O(n)
+*/
+function solution(gems) {
+  const gemTypeLength = new Set(gems).size;
+  const gemMap = new Map();
+  const gemRanges = [];
+
+  for (const [idx, gem] of gems.entries()) {
+    gemMap.delete(gem);
+    gemMap.set(gem, idx);
+
+    if (gemTypeLength === gemMap.size)
+      gemRanges.push({        
+        start: gemMap.values().next().value + 1,
+        end: idx + 1
+      });    
+  }  
+
+  gemRanges.sort((a, b) => {
+    return (a.end - a.start) === (b.end - b.start)
+      ? a.end - b.end
+      : (a.end - a.start) - (b.end - b.start);
+  })
+
+  return [
+    gemRanges[0].start,
+    gemRanges[0].end
+  ];
+}
+```
+
 </details>
 
 <hr/>
 
 ## 참고 문헌
 
-[Window Sliding Technique](https://www.geeksforgeeks.org/window-sliding-technique/) ━ *GeeksforGeeks*
\ No newline at end of file
+[Window Sliding Technique](https://www.geeksforgeeks.org/window-sliding-technique/) ━ *GeeksforGeeks*
+
+[Simple Solution at 보석 쇼핑](https://school.programmers.co.kr/learn/courses/30/lessons/67258/solution_groups?language=javascript&type=all) ━ *Programmers*
\ No newline at end of file

From c9a5af007a54f9f41d30256b3751aec88855c27a Mon Sep 17 00:00:00 2001
From: Brave Kim <ygflove@bible.ac.kr>
Date: Sat, 16 Jul 2022 18:41:17 +0900
Subject: [PATCH 10/10] :white_check_mark: Solve 1763

---
 15/yongki/SlidingWindow.md | 67 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 65 insertions(+), 2 deletions(-)

diff --git a/15/yongki/SlidingWindow.md b/15/yongki/SlidingWindow.md
index 9368d66..7413d12 100644
--- a/15/yongki/SlidingWindow.md
+++ b/15/yongki/SlidingWindow.md
@@ -244,8 +244,6 @@ var isZeroDivisor = function (num, target) {
     Output:   "cC"
     Expected: "cChH"
 
-### 문제 풀이
-
 ```js
 /**
  * @param {string} s
@@ -299,6 +297,69 @@ var longestNiceSubstring = function (s) {
 };
 ```
 
+### 문제 풀이
+
+분할 정복 방법으로 해결하는 풀이었다.    
+
+```js
+/**
+ * @param {string} s
+ * @return {string}
+ *
+ * m as nice substring
+ * n as string
+ * 
+ * time:  O(n²)
+ * space: O(mn)
+ */
+var longestNiceSubstring = function (s) {
+  const N = s.length;
+  const set = new Set();
+  let longestSize = 0;
+
+  for (let i = 0; i < N; i++) {
+    for (let j = i; j < N; j++) {
+      const substring = s.slice(i, j + 1);
+
+      if (isNiceSubstring(substring)) {
+        set.add(substring);
+        longestSize = Math.max(longestSize, substring.length);
+      }
+    }
+  }
+
+  for (const each of set) {
+    if (each.length === longestSize)
+      return each;
+  }
+
+  return '';
+};
+
+function isNiceSubstring(letters) {
+  let lower = new Set();
+  let upper = new Set();
+
+  for (const letter of letters) {
+    isLowerCaseLetter(letter) ? lower.add(letter) : upper.add(letter);
+  }
+
+  for (const each of lower) {
+    if (!upper.has(each.toUpperCase())) return false;
+  }
+
+  for (const each of upper) {
+    if (!lower.has(each.toLowerCase())) return false;
+  }
+
+  return true;
+}
+
+function isLowerCaseLetter(letter) {
+  return letter === letter.toLowerCase();
+}
+```
+
 </details>
 
 <details>
@@ -495,4 +556,6 @@ function solution(gems) {
 
 [Window Sliding Technique](https://www.geeksforgeeks.org/window-sliding-technique/) ━ *GeeksforGeeks*
 
+[Simple Solution at 1763. Longest Nice Substring](https://leetcode.com/problems/longest-nice-substring/discuss/1076734/javascript-direct-way-200ms) ━ *Leetcode*
+
 [Simple Solution at 보석 쇼핑](https://school.programmers.co.kr/learn/courses/30/lessons/67258/solution_groups?language=javascript&type=all) ━ *Programmers*
\ No newline at end of file