백준 17266

package baekjoon.이분탐색;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

class Main17266 {

   static int N, M;
   static int[] A;

   public static void main(String[] args) throws Exception {
      input();
      go();
   }

   private static void go() {
      int L = 0, R = N, ans = N;
      while (L <= R) {
         int mid = (L + R) / 2;
         if (determination(mid)) {
            ans = mid;
            R = mid - 1;
         } else {
            L = mid + 1;
         }
      }
      System.out.println(ans);
   }

   private static boolean determination(int h) {
      int last = 0;
      for (int i = 1; i <= M; i++) {
         if (A[i] - last <= h) {
            last = h + A[i];
         } else {
            return false;
         }

      }
      return last >= N;
   }

   private static void input() throws IOException {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st;
      N = Integer.parseInt(br.readLine());
      M = Integer.parseInt(br.readLine());
      A = new int[M + 1];
      st = new StringTokenizer(br.readLine());
      for (int i = 1; i <= M; i++) {
         A[i] = Integer.parseInt(st.nextToken());
      }
   }
}