diff --git a/LeetCode/Binary_Search/Find K-th Smallest Pair Distance/inudev5.kt b/LeetCode/Binary_Search/Find K-th Smallest Pair Distance/inudev5.kt
new file mode 100644
index 000000000..c0028ffc4
--- /dev/null
+++ b/LeetCode/Binary_Search/Find K-th Smallest Pair Distance/inudev5.kt	
@@ -0,0 +1,28 @@
+class Solution {
+    fun smallestDistancePair(nums: IntArray, k: Int): Int {
+        //pick two regardlesss of order
+        val n = nums.size
+
+        fun count(dist:Int, k:Int):Boolean{ //using two pointer two count number of valid distances
+            var (l,r,count) = listOf(0,0,0)
+            while(l<n){
+                while(r<n && nums[r]-nums[l]<=dist)r++
+                count+= r-l-1
+                l++
+            }
+            return count>=k
+        }
+        nums.sort()
+
+        var l = 0
+        var r = nums[n-1]-nums[0]
+
+        while(l<r){
+            val mid=l+(r-l)/2
+            //k개 이상임
+            if(count(mid,k)) r=mid
+            else l=mid+1
+        }
+        return l
+    }
+}
diff --git a/LeetCode/Binary_Search/Kth Smallest Number in Multiplication Table/inudev5.kt b/LeetCode/Binary_Search/Kth Smallest Number in Multiplication Table/inudev5.kt
new file mode 100644
index 000000000..940bfb391
--- /dev/null
+++ b/LeetCode/Binary_Search/Kth Smallest Number in Multiplication Table/inudev5.kt	
@@ -0,0 +1,20 @@
+class Solution {
+    fun findKthNumber(m: Int, n: Int, k: Int): Int {
+        //k번째 작은수
+        // mat[i][j] = (i+1)*(j+1)
+        var l = 1
+        var r = m*n
+        fun count(x:Int,k:Int):Boolean{ //if x has k or more values less than it
+            var count=0
+            for(i in 1..m)count+= minOf(x/i,n) //col에서 가능한 count
+            return count>=k
+        }
+        while(l<r){
+            val mid = l+(r-l)/2
+            if(count(mid,k)) r=mid
+            else l=mid+1
+        }
+        return l
+
+    }
+}
\ No newline at end of file
diff --git a/LeetCode/Binary_Search/Maximum Number of Events That Can Be Attended II/inudev5-iterative.kt b/LeetCode/Binary_Search/Maximum Number of Events That Can Be Attended II/inudev5-iterative.kt
new file mode 100644
index 000000000..b62a7338f
--- /dev/null
+++ b/LeetCode/Binary_Search/Maximum Number of Events That Can Be Attended II/inudev5-iterative.kt	
@@ -0,0 +1,24 @@
+class Solution {
+    fun maxValue(events: Array<IntArray>, k: Int): Int {
+
+        events.sortBy{it[0]}//시작일,종료일로 정렬
+        val n = events.size
+        // val lastDay=events[n-1][1]
+        val dp = Array(n+1){IntArray(k+1)}
+        fun upperBound(events:Array<IntArray>, start:Int, target:Int):Int{
+            var l=start
+            var r= events.size
+            while(l<r){
+                val mid = l+(r-l)/2
+                if(events[mid][0]<=target)l=mid+1
+                else r=mid
+            }
+            return r
+        }
+        for(i in n-1 downTo 0){
+            val next = upperBound(events,i+1,events[i][1])
+            for(j in 1..k)dp[i][j] = maxOf(dp[i+1][j], events[i][2]+dp[next][j-1])
+        }
+        return dp[0][k]
+    }
+}
\ No newline at end of file
diff --git a/LeetCode/Binary_Search/Maximum Number of Events That Can Be Attended II/inudev5.kt b/LeetCode/Binary_Search/Maximum Number of Events That Can Be Attended II/inudev5.kt
new file mode 100644
index 000000000..0f06ca9fd
--- /dev/null
+++ b/LeetCode/Binary_Search/Maximum Number of Events That Can Be Attended II/inudev5.kt	
@@ -0,0 +1,31 @@
+class Solution {
+    //top-down memoization
+    fun maxValue(events: Array<IntArray>, k: Int): Int {
+        //(시작 ,종료,보상) 종료일+1부터 다음 이벤트
+        //k개를 골랐을 때 maxSum
+        // var r = events.sumOf{it[2]}
+        events.sortBy{it[0]}//시작일로 정렬(이분탐색 대상이 시작일이기 때문)
+        val n = events.size
+        // val lastDay=events[n-1][1]
+        val dp = Array(n+1){IntArray(k+1){-1}}
+        fun upperBound(events:Array<IntArray>, start:Int, target:Int):Int{
+            var l=start
+            var r= events.size
+            while(l<r){
+                val mid = l+(r-l)/2 //l+(r-l+1)/2는 TLE가 난다. 2개 남았을 때를 생각하면됨
+                if(events[mid][0]<=target)l=mid+1
+                else r=mid
+            }
+            return r
+        }
+        fun solve(idx:Int, k:Int):Int{
+            if(idx>=n || k==0)return 0
+            if(dp[idx][k]!=-1)return dp[idx][k]
+            val next = upperBound(events,idx+1,events[idx][1])
+            dp[idx][k] = maxOf(solve(idx+1,k), events[idx][2]+solve(next,k-1))
+            return dp[idx][k]
+        }
+
+        return solve(0,k)
+    }
+}
\ No newline at end of file
diff --git a/LeetCode/Binary_Search/Shortest Distance to Target Color/inudev5.kt b/LeetCode/Binary_Search/Shortest Distance to Target Color/inudev5.kt
new file mode 100644
index 000000000..3f3ac455b
--- /dev/null
+++ b/LeetCode/Binary_Search/Shortest Distance to Target Color/inudev5.kt	
@@ -0,0 +1,39 @@
+class Solution {
+    //solution using binary search
+    fun shortestDistanceColor(colors: IntArray, queries: Array<IntArray>): List<Int> {
+        val map = hashMapOf<Int,MutableList<Int>>()
+        for(i in colors.indices){
+            map.putIfAbsent(colors[i], mutableListOf<Int>())
+            map[colors[i]]!!.add(i)
+        }
+        val res = mutableListOf<Int>()
+        fun lowerBound(arr:MutableList<Int>, target:Int):Int{
+            var l=0
+            var r=arr.size
+            while(l<r){
+                val mid= l+(r-l)/2
+                when{
+                    arr[mid]>=target -> r=mid
+                    else -> l=mid+1
+                }
+            }
+            return l
+        }
+        for((idx,color) in queries){
+            if(color !in map){res.add(-1);continue}
+            val idxList = map[color]!!
+            val pos = lowerBound(idxList,idx) //idx 이상인 최소 인덱스
+            when{
+                pos==idxList.size -> res.add(idx-idxList[idxList.lastIndex])
+                pos==0 -> res.add(idxList[0]-idx)
+                else-> {
+                    val left = idx-idxList[pos-1]
+                    val right = idxList[pos]-idx
+                    res.add(minOf(left,right))
+                }
+            }
+        }
+
+        return res
+    }
+}
\ No newline at end of file
diff --git a/LeetCode/Union_Find/Lexicographically Smallest Equivalent String/inudev5.kt b/LeetCode/Union_Find/Lexicographically Smallest Equivalent String/inudev5.kt
new file mode 100644
index 000000000..9c4098a13
--- /dev/null
+++ b/LeetCode/Union_Find/Lexicographically Smallest Equivalent String/inudev5.kt	
@@ -0,0 +1,41 @@
+class Solution {
+    class UnionFind(size:Int){
+        val root:IntArray by lazy { IntArray(size){it} }
+
+
+        fun union(x:Int, y:Int):Boolean{
+            val rootX = find(x)
+            val rootY = find(y)
+            if(rootX!=rootY){
+                when{
+                    rootX>rootY -> root[rootX] = rootY
+                    rootX<rootY -> root[rootY] = rootX
+                }
+                return true
+            }
+            return false
+        }
+        fun find(x:Int):Int{
+            if(x==root[x])return x
+            root[x] = find(root[x])
+            return root[x]
+            val set = hashSetOf(intArrayOf(1,2,3,4))
+            
+        }
+
+    }
+
+    fun smallestEquivalentString(s1: String, s2: String, baseStr: String): String {
+        val n = s1.length
+        val unionfind = UnionFind(26)
+        for(i in 0..n-1){
+            unionfind.union(s1[i]-'a', s2[i]-'a')
+        }
+        var res = ""
+        for(i in baseStr.indices){
+            val num = unionfind.find(baseStr[i]-'a')
+            res += (num+'a'.toInt()).toChar()
+        }
+        return res
+    }
+}
\ No newline at end of file
diff --git a/LeetCode/Union_Find/Sentent Similarity 2/inudev5.kt b/LeetCode/Union_Find/Sentent Similarity 2/inudev5.kt
new file mode 100644
index 000000000..8b2ca832e
--- /dev/null
+++ b/LeetCode/Union_Find/Sentent Similarity 2/inudev5.kt	
@@ -0,0 +1,51 @@
+class Solution {
+    class UnionFind(sentence:List<List<String>>){
+
+        val root:HashMap<String, String> by lazy {
+            val map =hashMapOf<String,String>()
+            for((a,b) in sentence){map.putIfAbsent(a,a);map.putIfAbsent(b,b)}
+            map
+        }
+        val rank:HashMap<String, Int> by lazy {
+            val map =hashMapOf<String, Int>()
+            root.keys.forEach{key-> map.put(key,1)}
+            map
+        }
+
+        //node가 String인 경우
+
+
+        fun union(x:String, y:String):Boolean{
+            val rootX = find(x)
+            val rootY = find(y)
+            if(rootX!=rootY){
+                when{
+                    rank[rootX]!!>rank[rootY]!! -> root[rootY] = rootX
+                    rank[rootX]!!<rank[rootY]!! -> root[rootX] = rootY
+                    else->{
+                        root[rootX] = rootY
+                        rank.put(rootY, rank.getOrDefault(rootY,1)+1)
+                    }
+                }
+                return true
+            }
+            return false
+        }
+        fun find(word:String):String{
+            if(word==root[word])return word
+            root[word] = find(root.getValue(word))
+            return root.getValue(word)
+        }
+    }
+    fun areSentencesSimilarTwo(sentence1: Array<String>, sentence2: Array<String>, similarPairs: List<List<String>>): Boolean {
+        if(sentence1.size!=sentence2.size)return false
+        val unionfind = UnionFind(similarPairs)
+        for((a,b) in similarPairs)unionfind.union(a,b)
+        for(i in sentence1.indices){
+            if(sentence1[i]==sentence2[i])continue
+            if(unionfind.root[sentence1[i]]==null ||unionfind.root[sentence2[i]]==null) return false
+            if(unionfind.find(sentence1[i])!=unionfind.find(sentence2[i]))return false
+        }
+        return true
+    }
+}
\ No newline at end of file
diff --git a/LeetCode/Union_Find/The Earliest Moment When Everyone Become Friends/inudev5.kt b/LeetCode/Union_Find/The Earliest Moment When Everyone Become Friends/inudev5.kt
new file mode 100644
index 000000000..67bbb6962
--- /dev/null
+++ b/LeetCode/Union_Find/The Earliest Moment When Everyone Become Friends/inudev5.kt	
@@ -0,0 +1,39 @@
+class Solution {
+    class UnionFind(size:Int){
+        val root:IntArray by lazy { IntArray(size){it} }
+        val rank:IntArray by lazy { IntArray(size){1} }
+
+        fun union(x:Int, y:Int):Boolean{
+            val rootX = find(x)
+            val rootY = find(y)
+            if(rootX!=rootY){
+                when{
+                    rank[rootX]>rank[rootY] -> root[rootY] = rootX
+                    rank[rootX]<rank[rootY]-> root[rootX]= rootY
+                    else->{
+                        root[rootY]= rootX
+                        rank[rootX]+=1
+                    }
+                }
+                return true
+            }
+            return false
+        }
+        fun find(x:Int):Int{
+            if(x==root[x])return x
+            root[x] = find(root[x])
+            return root[x]
+        }
+    }
+    fun earliestAcq(logs: Array<IntArray>, n: Int): Int {
+        val uf=UnionFind(n)
+        var prestamp = 0
+        var count=n
+        logs.sortBy({it[0]})
+        for((timestamp,a,b) in logs){
+            if(uf.union(a,b))count-=1
+            if(count==1)return timestamp
+        }
+        return -1
+    }
+}
\ No newline at end of file