提出 #3062027

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ソースコード 拡げる

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

#define reps(i,a,b) for(int (i)=(a); (i)<(b); ++(i))
#define rep(i,n) reps(i,0,(n))
#define chmax(x,y) x=max(x,y)
#define P(p) cout << (p) << endl;

ll N,M,X[100100];

bool tenken(ll minute) {
  ll left = -1;
  rep(i,M) {
    ll c = X[i]-1;
    if (c <= left) {
      chmax(left,c+minute);
    } else {
      if (c-left-1 > minute) return false;
      ll r1 = minute - c + 2 * (left+1);
      ll r2 = (minute + c + left + 1) / 2;
      chmax(left,max(r1,r2));
    }
  }
  return left>=N-1;
}

signed main() {
  cin >> N >> M;
  rep(i,M) cin >> X[i];
  ll low = 0, high = 2 * N;
  while (low<=high) {
    ll mid = (low + high) / 2;
    if (tenken(mid)) {
      high = mid - 1;
    } else {
      low = mid + 1;
    }
  }
  P(low);
}

提出情報

ジャッジ結果