diff --git a/src/problem1.js b/src/problem1.js
index 9a14f2c..ad1b464 100644
--- a/src/problem1.js
+++ b/src/problem1.js
@@ -1,6 +1,73 @@
 function problem1(pobi, crong) {
   var answer;
+  var n1;
+  var n2 = pobi[0];
+  var sum = 0;
+  var mul = 1;
+
+  if(pobi[0]+1 != pobi[1] || crong[0]+1 != crong[1]){
+    answer = -1;
+    return answer;
+  }
+
+  while(n2!=0){
+    n1 = n2 % 10;
+    n2 = Math.floor(n2 / 10);
+
+    sum = sum + n1;
+    mul = mul * n1;
+  }
+  var leftP = Math.max(sum, mul); //포비 왼쪽에서 큰 값
+
+  n2 = pobi[1];
+  sum = 0;
+  mul = 1;
+  while(n2!=0){
+    n1 = n2 % 10;
+    n2 = Math.floor(n2 / 10);
+
+    sum = sum + n1;
+    mul = mul * n1;
+  }
+  var rightP = Math.max(sum, mul); //포비 오른쪽에서 큰 값
+
+  n2 = crong[0];
+  sum = 0;
+  mul = 1;
+  while(n2!=0){
+    n1 = n2 % 10;
+    n2 = Math.floor(n2 / 10);
+
+    sum = sum + n1;
+    mul = mul * n1;
+  }
+  var leftC = Math.max(sum, mul); //크롱 왼쪽에서 큰 값
+
+  n2 = crong[1];
+  sum = 0;
+  mul = 1;
+  while(n2!=0){
+    n1 = n2 % 10;
+    n2 = Math.floor(n2 / 10);
+
+    sum = sum + n1;
+    mul = mul * n1;
+  }
+  var rightC = Math.max(sum, mul); //크롱 오른쪽에서 큰 값
+
+  pobi = Math.max(leftP, rightP);
+  crong = Math.max(leftC, rightC);
+
+  if(pobi>crong){
+    answer = 1;
+  }
+  else if(pobi<crong){
+    answer = 2;
+  }
+  else if(pobi==crong){
+    answer = 0;
+  }
   return answer;
 }
 
-module.exports = problem1;
+module.exports = problem1;
\ No newline at end of file
diff --git a/src/problem2.js b/src/problem2.js
index cebd07c..24854da 100644
--- a/src/problem2.js
+++ b/src/problem2.js
@@ -1,5 +1,23 @@
 function problem2(cryptogram) {
   var answer;
+  var word = "";
+  var string = cryptogram.split("");
+  var strlen = 0;
+
+  while(string.length!=strlen){
+    strlen = string.length;
+    for(var i=1; i<string.length; i++){
+      if(string[i-1] == string[i]){
+        string.splice(i-1, 2);
+      }
+    }
+  }
+
+  for(var j=0; j<string.length; j++){
+    word = word + string[j];
+  }
+  answer = word;
+
   return answer;
 }
 
diff --git a/src/problem3.js b/src/problem3.js
index 1baed28..c478f04 100644
--- a/src/problem3.js
+++ b/src/problem3.js
@@ -1,6 +1,22 @@
 function problem3(number) {
   var answer;
+  var n1;
+  var n2;
+  var count = 0;
+  var d = 0;
+  for(var i=1; i<number+1; i++){
+    n2 = i;
+
+    while(n2!=0){
+      n1 = n2 % 10;
+      if(n1==3 || n1==6 || n1==9){
+        count++;
+      }
+      n2 = Math.floor(n2 / 10);
+    }
+    
+  }
+  answer = count;
   return answer;
 }
-
 module.exports = problem3;
diff --git a/src/problem4.js b/src/problem4.js
index ee1d3bd..e5dc7ba 100644
--- a/src/problem4.js
+++ b/src/problem4.js
@@ -1,5 +1,27 @@
 function problem4(word) {
   var answer;
+  var wordList = word.split("");
+  var n;
+  var changedWord = "";
+  for(var i=0; i<wordList.length; i++){
+    if(wordList[i]==" "){
+      continue;
+    }
+    if(wordList[i].charCodeAt()>=97 && wordList[i].charCodeAt()<=122){
+      n = wordList[i].charCodeAt() - 97;
+      wordList[i] = String.fromCharCode(122 - n);
+    }
+
+    else if(wordList[i].charCodeAt()>=65 && wordList[i].charCodeAt()<=90){
+      n = wordList[i].charCodeAt() - 65;
+      wordList[i] = String.fromCharCode(90 - n);
+    }
+  }
+  for(var j=0; j<wordList.length; j++){
+    changedWord = changedWord + wordList[j];
+  }
+
+  answer = changedWord;
   return answer;
 }
 
diff --git a/src/problem5.js b/src/problem5.js
index 9368e87..164dbd5 100644
--- a/src/problem5.js
+++ b/src/problem5.js
@@ -1,5 +1,45 @@
 function problem5(money) {
   var answer;
+  var n1;
+  var n2 = money;
+  var change;
+  var moneyList = [0, 0, 0, 0, 0, 0, 0, 0, 0];
+  var i = 8;
+  while(i>=0){
+    n1 = n2 % 10;
+    if(i==8){
+      moneyList[i] = n1;
+    }
+    else if(i%2==1){
+      change = n1;
+      while(change>=5){
+        change = change % 5;
+        moneyList[i-1]++;
+      }
+      moneyList[i] = change;
+      i--;
+    }
+    else if(i%2==0){
+      if(i==0){
+        moneyList[i] = moneyList[i] + n1;
+      }
+      else{
+        change = n1;
+        if(change>=2){
+          while(change>=2){
+            change = change % 2;
+            moneyList[i-1]++;
+          }
+        }
+        moneyList[i] = change;
+        i--;
+      }
+    }
+    n2 = Math.floor(n2 / 10);
+    i--;
+  }
+
+  answer = moneyList;
   return answer;
 }
 
diff --git a/src/problem6.js b/src/problem6.js
index 3f842b5..8f7e43c 100644
--- a/src/problem6.js
+++ b/src/problem6.js
@@ -1,6 +1,33 @@
 function problem6(forms) {
-  var answer;
+  var answer = [];
+  var info = new Map();
+  var same;
+  var sameSet = new Set();
+  var dup = new Map();
+  for(const [email, name] of forms) {
+    info.set(email, name);
+  }
+
+  for(var [email, name] of info){
+    for (var i=0; i<name.length-1; i++) {
+      for (var j=2; j<=name.length-i; j++) {
+        same = name.slice(i, i+j);
+
+        if (dup.has(same)) {
+          sameSet.add(dup.get(same));
+          sameSet.add(email);
+        }
+        else{
+          dup.set(same, email);
+        }
+      }
+    }
+  }
+  for(let email of sameSet){
+    answer.push(email);
+  }
+  answer = answer.sort();
   return answer;
 }
 
-module.exports = problem6;
+module.exports = problem6;
\ No newline at end of file
diff --git a/src/problem7.js b/src/problem7.js
index ee1bb9d..7071263 100644
--- a/src/problem7.js
+++ b/src/problem7.js
@@ -1,5 +1,66 @@
 function problem7(user, friends, visitors) {
-  var answer;
+  var answer = [];
+  var userFriends = new Set();
+  var score = new Map();
+  var name = [];
+  for(var i=0; i<friends.length; i++){
+    if(friends[i][0]==user){
+      userFriends.add(friends[i][1]);
+    }
+    if(friends[i][1]==user){
+      userFriends.add(friends[i][0]);
+    }
+  }
+  
+  for(var k=0; k<friends.length; k++){
+    if(userFriends.has(friends[k][0])){
+      if(friends[k][1]==user){
+        continue;
+      }
+      if(score.has(friends[k][1])){
+        var n = score.get(friends[k][1]);
+        score.delete(friends[k][1]);
+        score.set(friends[k][1], n+=10);
+      }
+      else{
+        score.set(friends[k][1], 10);
+      }
+    }
+
+    if(userFriends.has(friends[k][1])){
+      if(friends[k][0]==user){
+        continue;
+      }
+      if(score.has(friends[k][1])){
+        var n = score.get(friends[k][1]);
+        score.delete(friends[k][1]);
+        score.set(friends[k][1], n+=10);
+      }
+      else{
+        score.set(friends[k][1], 10);
+      }
+    }
+  }
+
+  for(var j=0; j<visitors.length; j++){
+    if(userFriends.has(visitors[j])){
+      continue;
+    }
+    if(score.has(visitors[j])){
+      var n = score.get(visitors[j]);
+      score.delete(visitors[j]);
+      score.set(visitors[j], n+=1);
+    }
+    else{
+      score.set(visitors[j], 1);
+    }
+  }
+
+  name = Array.from(score);
+  name.sort((a, b) => b[1] - a[1] || a[0].localeCompare(b[0]));
+  for(var l=0; l<score.size; l++){
+    answer.push(name[l][0]);
+  }
   return answer;
 }