AtCoder Beginner Contest 161

AtCoder Beginner Contest 161

https://atcoder.jp/contests/abc161
这套不算难，但是sb我还是写不出来是为什么呢
F是个妙妙题

C - Replacing Integer

WA了一次所以放上来

#include <bits/stdc++.h>
#define ll long long

using namespace std;

int main () {
    ll a, b;
    cin >> a >> b;
    if (a > b)  a %= b;
    if (a < abs (a - b))    cout << a;
    else    cout << abs (a - b);
}

D - Lunlun Number

队列模拟

#include <bits/stdc++.h>
#define ll long long

using namespace std;
int k;

int main () {
    queue<ll>q;
    for (int i = 1; i <= 9; i++)    q.push(i);
    cin >> k;
    k--;
    while (k--) {
        ll t = q.front();
        int d = t % 10;
        q.pop ();
        ll tt = t * 10 + d;
        if (d != 0) q.push (tt - 1);
        q.push (tt);
        if (d != 9) q.push (tt + 1);
    }
    cout << q.front ();
}

E - Yutori

正向贪心 + 逆向贪心

#include <bits/stdc++.h>
#define ll long long

using namespace std;
const int N = 2e5 + 5;
int n, k, c, l[N], r[N];
string s;

int main () {
    cin >> n >> k >> c >> s;
    s = ' ' + s;
    vector<int> v1, v2;
    int lst = -1e9;
    for (int i = 1; i <= n; i++) {
        l[i] = l[i-1];
        if (s[i] == 'o' && i - lst > c)    l[i]++, lst = i;
    }
    lst = 1e9;
    for (int i = n; i >= 1; i--) {
        r[i] = r[i+1];
        if (s[i] == 'o' && lst - i > c)    r[i]++, lst = i;
    }
    //for (int i = 1; i <= n; i++)   cout << l[i] << ' ';cout << endl;
    //for (int i = 1; i <= n; i++)   cout << r[i] << ' ';cout << endl;
    for (int i = 1; i <= n; i++) {
        if (s[i] == 'x')    continue;
        if (l[i-1] + r[i+1] + 1 == k)   cout << i << endl;
    }
}

F - Division or Subtraction

根号分治

#include <bits/stdc++.h>
#define ll long long

using namespace std;

int main () {
    ll n, ans = 0;
    cin >> n;
    //根号分治: n = k^x(ky+1)
    if (n == 2) {
        cout << 1;
        return 0;
    }
    
    for (ll i = 2; i * i <= n; i++) {
        //k>sqrt(n) -> n % k = 1, k|(n-1)
        if ((n - 1) % i == 0) {
            ans ++;
            if (i * i != n - 1) ans ++;
        }
        //k<=sqrt(n) -> 暴力除k
        ll m = n;
        while (m % i == 0)  m /= i;
        if (m != n && m % i == 1)   ans++;
    }
    cout << ans + 2; //y = 0, n自身
}

//由根号断开