[20250212] BOJ / 골드3 / K진 트리 / 이강현

lkhyun/202502/12 BOJ 골드3 K진 트리.md

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+```java
+import java.util.*;
+import java.io.*;
+public class Main{
+    public static void main(String[] args) throws Exception{
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        long N = Long.parseLong(st.nextToken());
+        long K = Integer.parseInt(st.nextToken());
+        long Q = Integer.parseInt(st.nextToken());
+
+        for(int i=0;i<Q;i++){
+            st = new StringTokenizer(br.readLine());
+            long x = Long.parseLong(st.nextToken());
+            long y = Long.parseLong(st.nextToken());
+            long start = Math.min(x,y); //start를 작은걸로
+            long end = Math.max(x,y);   //end를 큰걸로 고정
+            if(K == 1){
+                bw.write((end-start)+"\n");
+                continue;
+            }
+            long startdepth = findDepth(start,K);
+            long enddepth = findDepth(end,K);
+            long depthDiff = enddepth - startdepth;
+            long dist = 0;
+            for(int j=0;j<depthDiff;j++){
+                end = findParent(end, K);
+                dist++;
+            }
+            while(start!=end){
+                start = findParent(start, K);
+                end = findParent(end, K);
+                dist+=2;
+            }
+            bw.write(dist+"\n");
+        }
+        bw.flush();
+    }
+    public static long findDepth(long x,long K){
+        long finder = 1;
+        long depth = 1;
+        while(x > finder){
+            finder *= K;
+            finder += 1;
+            depth++;
+        }
+        return depth;
+    }
+    public static long findParent(long x,long K){
+        if(x%K==0 || x%K==1){
+            return x/K;
+        }else{
+            return x/K + 1;
+        }
+    }
+}
+```