[20250723] BOJ / G5 / 핑거 스냅 / 이종환

Author: 0224LJH

0224LJH/202507/23 BOJ 핑거 스냅.md

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+```java
+import java.awt.*;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.*;
+
+
+public class Main {
+    static int tc,startNum, from,to;
+    static int[][] input;
+    static boolean[] primes = new boolean[1000001];
+    static int[] dp = new int[1000001];
+    static StringBuilder sb = new StringBuilder();
+
+    public static void main(String[] args) throws IOException {
+        init();
+        process();
+        print();
+    }
+
+    private static void init() throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        tc = Integer.parseInt(br.readLine());
+        input = new int[tc][3];
+
+        for (int i = 0; i < tc; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            for (int j = 0; j < 3; j++) {
+                input[i][j] = Integer.parseInt(st.nextToken());
+            }
+        }
+    }
+
+    private static void process() throws IOException {
+        makePrimeList();
+        for (int i = 0; i < tc; i++) {
+            startNum = input[i][0];
+            from  = input[i][1];
+            to   = input[i][2];
+
+            Arrays.fill(dp, -1);
+            doDp(startNum);
+            int count = Integer.MAX_VALUE;
+
+            for (int j = from; j <= to; j++){
+                if (dp[j] != -1 && primes[j]){
+                    count = Math.min(count, dp[j]);
+                }
+            }
+
+            sb.append( count==Integer.MAX_VALUE ? -1 : count).append("\n");
+        }
+    }
+
+    private static void doDp(int startNum) {
+        dp[startNum] = 0;
+        Queue<Integer> queue = new LinkedList<>();
+        queue.add(startNum);
+
+        while (!queue.isEmpty()) {
+            int cur = queue.poll();
+            int curCount = dp[cur];
+            if (cur + 1 <= 1000000 && dp[cur + 1] == -1) {
+                dp[cur + 1] = curCount + 1;
+                queue.add(cur+1);
+            }
+            if ( cur -1 > 0 && dp[cur - 1] == -1) {
+                dp[cur -1] = curCount + 1;
+                queue.add(cur-1);
+            }
+            if (cur /2 > 0 && dp[cur / 2] == -1) {
+                dp[cur /2] = curCount + 1;
+                queue.add(cur/2);
+            }
+            if (cur / 3 > 0 && dp[cur / 3] == -1) {
+                dp[cur / 3] = curCount + 1;
+                queue.add(cur/3);
+            }
+        }
+
+
+    }
+
+    private static void makePrimeList() {
+        Arrays.fill(primes, true);
+        primes[0] = false;
+        primes[1] = false;
+        for (int i = 2; i <= 1000000; i++) {
+            if (!primes[i]) continue;
+
+            int num = i * 2;
+            while (num <= 1000000) {
+                primes[num] = false;
+                num += i;
+            }
+        }
+    }
+
+
+    private static void print()  {
+        System.out.print(sb.toString());
+    }
+
+
+
+}
+
+
+```