[20250227] BOJ / P5 / 한동이는 영업사원! / 신희을

ShinHeeEul/202502/27 BOJ P5 한동이는 영업사원!.md

@@ -0,0 +1,151 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Solution {
+
+
+    static int N;
+    static int min = Integer.MAX_VALUE;
+    static ArrayList<Integer>[] lists;
+    static int[][] parents;
+    static int[] depths;
+    static boolean[] visited;
+    static int count = 0;
+    static int logN;
+
+    public static void main(String[] args) throws Exception {
+
+       N = read();
+
+       logN = (int) (Math.log(N) / Math.log(2));
+       lists = new ArrayList[N + 1];
+       visited = new boolean[N + 1];
+       parents = new int[N + 1][logN];
+       depths = new int[N + 1];
+
+       for(int i = 1; i < N + 1; i++) lists[i] = new ArrayList<>();
+
+       for(int i = 1; i < N; i++) {
+
+    	   int a = read();
+    	   int b = read();
+
+    	   lists[a].add(b);
+    	   lists[b].add(a);
+       }
+
+       // 1. dfs 돌면서 맵 만들기
+       dfs(1);
+       // 2. parents 배열 채우기
+       for(int i = 1; i < logN; i++) {
+    	   for(int j = 1; j <= N; j++) {
+    		   parents[j][i] = parents[parents[j][i - 1]][i - 1];
+    	   }
+       }
+
+       int current = 1;
+       int M = read();
+
+       for(int i = 0; i < M; i++) {
+           int destination = read();
+           int tmp = destination;
+
+           if(current == destination) continue;
+           // 3. 높이 맞추기
+           int dc = depths[current];
+           int dd = depths[destination];
+
+           if(dc < dd) {
+        	   int diff = dd - dc;
+        	   count += diff;
+        	   destination = up(destination, diff);
+           } else if(dd < dc) {
+        	   int diff = dc - dd;
+        	   count += diff;
+        	   current = up(current, diff);
+           }
+           // 4. lca
+           count += (lca(current, destination) << 1);
+           current = tmp;
+       }
+
+       System.out.println(count);
+
+    }
+
+    public static int lca(int a, int b) {
+    	// 제일 높은 거부터 하나씩 보면서
+    	int cnt = 0;
+    	for(int i = logN - 1; i >= 0; i--) {
+    		if(parents[a][i] == parents[b][i]) continue;
+
+    		a = parents[a][i];
+    		b = parents[b][i];
+
+    		cnt += Math.pow(2, i);
+    	}
+
+    	return a == b ? cnt : cnt + 1;
+
+    }
+
+    public static int up(int current, int diff) {
+    	for(int i = 0; (1 << i) <= diff; i++) {
+    		int bit = (1 << i);
+    		if((bit | diff) == diff) {
+    			current = parents[current][i];
+    		}
+    	}
+    	return current;
+    }
+
+    public static void dfs(int start) {
+    	Stack<Node> stack = new Stack<>();
+
+    	stack.add(new Node(start, 1));
+    	visited[start] = true;
+    	while(!stack.isEmpty()) {
+    		Node node = stack.pop();
+
+    		int val = node.val;
+    		int depth = node.depth;
+    		depths[val] = depth;
+
+    		for(int child : lists[val]) {
+    			if(visited[child]) continue;
+    			parents[child][0] = val;
+    			visited[child] = true;
+    			stack.add(new Node(child, depth + 1));
+    		}
+    	}
+    }
+
+    static class Node {
+    	int val;
+    	int depth;
+
+    	public Node(int val, int depth) {
+    		this.val = val;
+    		this.depth = depth;
+    	}
+    }
+
+    private static int read() throws Exception {
+        int d, o;
+        boolean negative = false;
+        d = System.in.read();
+
+        if (d == '-') {
+            negative = true;
+            d = System.in.read();
+        }
+        o = d & 15;
+
+        while ((d = System.in.read()) > 32)
+            o = (o << 3) + (o << 1) + (d & 15);
+
+        return negative? -o:o;
+    }
+}
+```