Educational Codeforces Round 82 (Rated for Div. 2)部分题解

Problem A

找到最前面和最后面的1，计算中间需要填的坑就可以了。

Problem B

数学题，老数学废物了，看代码吧，不知道咋讲，寄几推一个就可以了。

t=int (input ())
for _ in range (t):
    st=list (map (int,input ().split ()))
    n=(st[0]+1)//2
    x=n//st[1]; y=n%st[1]
    if (y==0):
        y=st[1]
        x-=1
    ans=max (st[0],x*(st[1]+st[2])+y)
    print (int (ans))

Problem C

是这样的，首先的话，在键盘中一个字母只能出现一次，然后一个字母最多只能有两个adj字母，而且我们password里面必须是有两个只有一个adj元素，这两个条件用来判断是否可以成功构造，接下来就是类似模拟？反正你STL XJB搞就好了。

#include<cstdio>
#include<algorithm>
#include<vector>
#include<queue>
#include<set>
#include<map>
#include<iostream>
#include<cstring>
#include<cmath>
using namespace std;
#define rep(i,f_start,f_end) for (int i=f_start;i<=f_end;++i)
#define per(i,n,a) for (int i=n;i>=a;i--)
#define MT(x,i) memset(x,i,sizeof(x) )
#define rev(i,start,end) for (int i=start;i<end;i++)
#define inf 0x3f3f3f3f
#define mp(x,y) make_pair(x,y)
#define lowbit(x) (x&-x)
#define MOD 1000000007
#define exp 1e-8
#define N 1000005 
#define fi first 
#define se second
#define pb push_back
typedef long long ll;
const ll INF=0x3f3f3f3f3f3f3f3f;
typedef vector <int> VI;
typedef pair<int ,int> PII;
typedef pair<int ,PII> PIII;
ll gcd(ll a,ll b){return b==0?a:gcd(b,a%b);}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;};
void check_max (int &a,int b) { a=max (a,b);}
void check_min (int &a,int b) { a=min (a,b);}
inline int read() {
    char ch=getchar(); int x=0, f=1;
    while(ch<'0'||ch>'9') {
        if(ch=='-') f=-1;
        ch=getchar();
    } while('0'<=ch&&ch<='9') {
        x=x*10+ch-'0';
        ch=getchar();
    } return x*f;
}

const int maxn=1e6+10;
string str;
int n;

void solve () {
    cin>>str;
    map <char,set<char> > mp;
    int flag=0;
    rev (i,0,str.size ()) {
        if (i==0) mp[str[i]].insert (str[i+1]);
        else if (i==(str.size ()-1)) mp[str[i]].insert (str[i-1]);
        else mp[str[i]].insert (str[i-1]),mp[str[i]].insert (str[i+1]);
    }
    char st='#',ed='#';
    int sign=0;
    for (auto it:mp) {
        if (it.second.size ()>=3) flag=1;
        if (it.second.size ()==1&&sign==0) st=it.first,sign=1;
        if (it.second.size ()==1) ed=it.first;
    }
    string ans="";
    if (flag||st=='#'||ed=='#')  cout<<"NO"<<endl;
    else {
        cout<<"YES"<<endl;
        set <char> s;
        ans+=st;
        char temp=st;
        s.insert (st);
        while (mp[temp].size ()) {
            char sit='#';
            for (auto it:mp[temp]) {
                if (mp[it].size ()>1&&!s.count (it)) {
                    sit=it;
                    ans+=it;
                    s.insert (it);
                    break;
                }
            }
            temp=sit;
            if (sit=='#') break;
        }
        ans+=ed; s.insert (ed);
        for (char i='a';i<='z';i++) if (!s.count (i)) ans+=i;
        set <char> k;
        rev (i,0,ans.size ()) {
            if (k.count (ans[i])) ans.erase (ans.begin ()+i);
            else k.insert (ans[i]);
        }
        cout<<ans<<endl;
    }
    return ;
}

int main () {
    ios::sync_with_stdio (false);
    int t;
    cin>>t;
    while (t--) {
        solve ();
    }
    return 0;
}