牛客小白月赛97

比赛链接：牛客小白月赛97

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A

思路

       

代码

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 1e5 + 10;

int num[N];
int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    int a;
    cin >> a;
    num[a]++;
  }
  for (int i = 1; i <= 100; i++) {
    if (num[i] >= 3) {
      cout << "YES" << endl;
      return 0;
    }
  }
  cout << "NO" << endl;

  return 0;
}

---

B

思路

       

代码

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 1e5 + 10;

ll a[N];
int main() {
  int n, flag = 0;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
    if (a[i] == 0) {
      flag = 1;
    }
  }
  if (flag == 1)
    cout << "NO" << endl;
  else
    cout << "YES" << endl;
  return 0;
}

---

C

思路

       

代码

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 1e6 + 10;
const ll mod = 1e9 + 7;

ll qsm(ll x, ll y) {
  ll res = 1;
  while (y) {
    if (y & 1) {
      res *= x;
      res %= mod;
    }
    x *= x;
    x %= mod;
    y /= 2;
  }
  return res;
}

ll c(ll x, ll y) {
  ll res = 1;
  for (ll i = x + 1; i <= y; i++) {
    res *= i;
    res %= mod;
  }
  ll res2 = 1;
  for (ll i = y - x; i >= 1; i--) {
    res2 *= i;
    res2 %= mod;
  }
  res *= qsm(res2, mod - 2);
  res %= mod;
  return res;
}

int main() {
  int n, x;
  cin >> n >> x;
  ll now = pow(sqrt(x), 2), num = sqrt(x);
  if (num < n) {
    cout << 0 << endl;
    return 0;
  }
  ll res = 1;
  for (int i = num; i > n; i--) {
    res += c(n - 1, i - 1);
    res %= mod;
  }
  cout << res ;

  return 0;
}

---

D

思路

       

代码

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 1e2 + 10;
struct point{
    ll x, y, num;
};
int dis[10][2] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
ll a[N][N], c[N][N], dp[20][20][10010];
int main() {
    ll n, m, p;
    cin >> n >> m >> p;
    
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            for (int k = 0; k <= p; k++) {
                dp[i][j][k] = 1e9;
            }
        }
    }
    
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            cin >> a[i][j];
            a[i][j] %= (p - 1);
        }
    }
    
    for (int i =1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            cin >> c[i][j];
        }
    }

    
    queue<point>q;
    q.push({1, 1, a[1][1]});
    dp[1][1][a[1][1]] = 0;
    
    while (!q.empty()) {
        ll x = q.front().x, y = q.front().y, num = q.front().num;
        q.pop();
        for (int i = 0; i < 4; i++) {
            ll dx = x + dis[i][0], dy = y + dis[i][1];
            if (dx > n || dx < 1 || dy > m || dy < 1) continue;
            ll dnum = (num + a[dx][dy]) % (p - 1);
            if (dp[dx][dy][dnum] <= dp[x][y][num] + 1) continue;
            dp[dx][dy][dnum] = dp[x][y][num] + 1;
            q.push({dx, dy, dnum});
        }
    }

    if (dp[n][m][0] != 1e9) cout << dp[n][m][0];
    else cout << -1 << endl;
    
    return 0;
}

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E

思路

       

代码

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F

思路

       

代码