diff --git a/src/do02reen24/Review/additional-learning.md b/src/do02reen24/Review/additional-learning.md
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+++ b/src/do02reen24/Review/additional-learning.md
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+# 프로그래머스 추가학습
+
+# 난이도 1
+
+## 모의고사 42840
+
+# 난이도 2
+
+## 기능개발 42586
+
+- 처음에 실수로 반올림을 하여 결과가 틀렸었다. 함수를 올림으로 고쳐주어 해결할 수 있었다.
+
+## 다리를 지나는 트럭 42583
+
+- 이중 배열로도 가능했지만 가독성을 향상시키기 위해 class로 구현하여 풀었다.
+
+## 스킬트리 49993
+
+- map을 활용하여 사전 스킬들을 기록해주고 확인하였다.
+- 얕은 복사의 문제가 있어 `JSON.parse(JSON.stringify(arr))` 를 통해 깊은 복사를 처리해주었다.
+
+## 두 개 뽑아서 더하기 68644
+
+- object를 선언해서 해결하였다. 그러나 set을 써서 문제를 해결하였으면 더 쉬웠을 것 같다. set의 존재를 계속 까먹는데 잘 기억하자!!
diff --git a/src/do02reen24/brute-force/programmers_42840.js b/src/do02reen24/brute-force/programmers_42840.js
new file mode 100644
index 0000000..07a02a3
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+++ b/src/do02reen24/brute-force/programmers_42840.js
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+function getScore(answers, userAnswers) {
+  const userLength = userAnswers.length;
+  return answers.reduce((sum, value, index) => {
+    if (value === userAnswers[index % userLength]) return sum + 1;
+    return sum;
+  }, 0);
+}
+
+function solution(answers) {
+  const answer = [];
+  const ans1 = [1, 2, 3, 4, 5];
+  const ans2 = [2, 1, 2, 3, 2, 4, 2, 5];
+  const ans3 = [3, 3, 1, 1, 2, 2, 4, 4, 5, 5];
+
+  const score1 = getScore(answers, ans1);
+  const score2 = getScore(answers, ans2);
+  const score3 = getScore(answers, ans3);
+
+  const maxScore = Math.max(score1, score2, score3);
+
+  if (maxScore === score1) answer.push(1);
+  if (maxScore === score2) answer.push(2);
+  if (maxScore === score3) answer.push(3);
+  return answer;
+}
diff --git a/src/do02reen24/data-structure/programmers_42583.js b/src/do02reen24/data-structure/programmers_42583.js
new file mode 100644
index 0000000..ddf0b92
--- /dev/null
+++ b/src/do02reen24/data-structure/programmers_42583.js
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+class Bridge {
+  constructor(weight, remain) {
+    this.weight = weight;
+    this.remain = remain;
+  }
+
+  getRemain() {
+    return this.remain;
+  }
+
+  subRemain() {
+    this.remain--;
+  }
+}
+
+function sumBridge(bridge) {
+  return bridge.reduce((sum, now) => (sum += now.weight), 0);
+}
+
+function solution(bridge_length, weight, truck_weights) {
+  let time = 1;
+  let index = 0;
+  const bridges = [];
+  while (index < truck_weights.length) {
+    const remain = weight - sumBridge(bridges);
+    if (remain >= truck_weights[index]) {
+      bridges.push(new Bridge(truck_weights[index], bridge_length));
+      index++;
+    }
+    time++;
+    bridges.forEach((bridge) => bridge.subRemain());
+    if (bridges[0].getRemain() === 0) bridges.shift();
+  }
+  return time + bridge_length - 1;
+}
diff --git a/src/do02reen24/data-structure/programmers_42586.js b/src/do02reen24/data-structure/programmers_42586.js
new file mode 100644
index 0000000..872e879
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+++ b/src/do02reen24/data-structure/programmers_42586.js
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+function solution(progresses, speeds) {
+  let answer = [];
+  const finishDay = progresses.map((progress, index) =>
+    Math.ceil((100 - progress) / speeds[index])
+  );
+  let max;
+  let count = 0;
+
+  finishDay.forEach((element) => {
+    if (!max) max = element;
+    else if (max < element) {
+      answer.push(count);
+      count = 0;
+      max = element;
+    }
+    count++;
+  });
+  answer.push(count);
+  return answer;
+}
diff --git a/src/do02reen24/data-structure/programmers_49993.js b/src/do02reen24/data-structure/programmers_49993.js
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index 0000000..bcfec1d
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+++ b/src/do02reen24/data-structure/programmers_49993.js
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+function splitSkill(skill) {
+  return skill.split('');
+}
+
+function getBeforeSkill(skills) {
+  const beforeSkill = {};
+  skills.reduce((arr, now) => {
+    beforeSkill[now] = JSON.parse(JSON.stringify(arr));
+    arr.push(now);
+    return arr;
+  }, []);
+  return beforeSkill;
+}
+
+function isValid(tree, beforeSkill) {
+  const study = {};
+  for (let skill of tree) {
+    study[skill] = true;
+    if (!beforeSkill[skill]) continue;
+    for (let bSkill of beforeSkill[skill]) {
+      if (!study[bSkill]) return 0;
+    }
+  }
+  return 1;
+}
+
+function solution(skill, skill_trees) {
+  const beforeSkill = getBeforeSkill(splitSkill(skill));
+  return skill_trees.reduce(
+    (sum, tree) => sum + isValid(splitSkill(tree), beforeSkill),
+    0
+  );
+}
+
+console.log(solution('CBD', ['BACDE', 'CBADF', 'AECB', 'BDA']));
diff --git a/src/do02reen24/etc/programmers_68644.js b/src/do02reen24/etc/programmers_68644.js
new file mode 100644
index 0000000..af25033
--- /dev/null
+++ b/src/do02reen24/etc/programmers_68644.js
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+function sortAsc(a, b) {
+  return a - b;
+}
+
+function getKeys(dict) {
+  const keys = [];
+  for (const key in dict) keys.push(Number(key));
+  return keys.sort(sortAsc);
+}
+
+function solution(numbers) {
+  const dict = {};
+  for (let a = 0; a < numbers.length; a++) {
+    for (let b = a + 1; b < numbers.length; b++) {
+      const sum = numbers[a] + numbers[b];
+      dict[sum] = true;
+    }
+  }
+
+  return getKeys(dict);
+}