Educational Codeforces Round 32

A Local Extrema

水 

#include "iostream"
#include "iomanip"
#include "string.h"
#include "stack"
#include "queue"
#include "string"
#include "vector"
#include "set"
#include "map"
#include "algorithm"
#include "stdio.h"
#include "math.h"
#pragma comment(linker, "/STACK:102400000,102400000")
#define bug(x) cout<<x<<" "<<"UUUUU"<<endl;
#define mem(a,x) memset(a,x,sizeof(a))
#define step(x) fixed<< setprecision(x)<<
#define mp(x,y) make_pair(x,y)
#define pb(x) push_back(x)
#define ll long long
#define endl ("\n")
#define ft first
#define sd second
#define lrt (rt<<1)
#define rrt (rt<<1|1)
using namespace std;
const ll mod=1e9+7;
const ll INF = 1e18+1LL;
const int inf = 1e9+1e8;
const double PI=acos(-1.0);
const int N=1e5+100;

int n,ans,a[N];
int main(){
    ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
    cin>>n;
    for(int i=1; i<=n; ++i){
        cin>>a[i];
    }
    for(int i=2; i<n; ++i){
        if(a[i]>a[i-1] && a[i]>a[i+1]) ans++;
        if(a[i]<a[i-1] && a[i]<a[i+1]) ans++;
    }
    cout<<ans<<endl;
    return 0;
}

 

B Buggy Robot

水

#include "iostream"
#include "iomanip"
#include "string.h"
#include "stack"
#include "queue"
#include "string"
#include "vector"
#include "set"
#include "map"
#include "algorithm"
#include "stdio.h"
#include "math.h"
#pragma comment(linker, "/STACK:102400000,102400000")
#define bug(x) cout<<x<<" "<<"UUUUU"<<endl;
#define mem(a,x) memset(a,x,sizeof(a))
#define step(x) fixed<< setprecision(x)<<
#define mp(x,y) make_pair(x,y)
#define pb(x) push_back(x)
#define ll long long
#define endl ("\n")
#define ft first
#define sd second
#define lrt (rt<<1)
#define rrt (rt<<1|1)
using namespace std;
const ll mod=1e9+7;
const ll INF = 1e18+1LL;
const int inf = 1e9+1e8;
const double PI=acos(-1.0);
const int N=1e5+100;

char s[1005];
int l, r, u, d;
int main(){
    int n; cin>>n;
    cin>>s;
    int x=0, y=0, ans=0;
    for(int i=0; i<n; ++i){
        if(s[i]=='U') u++;
        if(s[i]=='D') d++;
        if(s[i]=='L') l++;
        if(s[i]=='R') r++;
    }
    cout<<(min(l,r)+min(u,d))*2;
    return 0;
}

 

C K-Dominant Character

水

#include "iostream"
#include "iomanip"
#include "string.h"
#include "stack"
#include "queue"
#include "string"
#include "vector"
#include "set"
#include "map"
#include "algorithm"
#include "stdio.h"
#include "math.h"
#pragma comment(linker, "/STACK:102400000,102400000")
#define bug(x) cout<<x<<" "<<"UUUUU"<<endl;
#define mem(a,x) memset(a,x,sizeof(a))
#define step(x) fixed<< setprecision(x)<<
#define mp(x,y) make_pair(x,y)
#define pb(x) push_back(x)
#define ll long long
#define endl ("\n")
#define ft first
#define sd second
#define lrt (rt<<1)
#define rrt (rt<<1|1)
using namespace std;
const ll mod=1e9+7;
const ll INF = 1e18+1LL;
const int inf = 1e9+1e8;
const double PI=acos(-1.0);
const int N=1e5+100;

int n, vis[300];
char s[N];
bool check(int x){
    mem(vis,0);
    for(int i=1; i<=x; ++i){
        vis[s[i]]++;
    }
    for(int i=1; i<=n-x; ++i){
        if(s[i]==s[i+x]) continue;
        if(vis[s[i+x]]>0) vis[s[i+x]]++;
        vis[s[i]]--;
    }
    for(int i='a'; i<='z'; ++i){
        if(vis[i]>0) return 1;
    }
    return 0;
}

int main(){
    cin>>s+1;
    n=strlen(s+1);
    int l=1, r=n, ans=n;
    while(l<=r){
        int mid=l+r>>1;
        if(check(mid)){
            ans=mid, r=mid-1;
        }
        else l=mid+1;
    }
    cout<<ans<<endl;
    return 0;
}

D Almost Identity Permutations

错排 水

#include "iostream"
#include "iomanip"
#include "string.h"
#include "stack"
#include "queue"
#include "string"
#include "vector"
#include "set"
#include "map"
#include "algorithm"
#include "stdio.h"
#include "math.h"
#pragma comment(linker, "/STACK:102400000,102400000")
#define bug(x) cout<<x<<" "<<"UUUUU"<<endl;
#define mem(a,x) memset(a,x,sizeof(a))
#define step(x) fixed<< setprecision(x)<<
#define mp(x,y) make_pair(x,y)
#define pb(x) push_back(x)
#define ll long long
#define endl ("\n")
#define ft first
#define sd second
#define lrt (rt<<1)
#define rrt (rt<<1|1)
using namespace std;
const ll mod=1e9+7;
const ll INF = 1e18+1LL;
const int inf = 1e9+1e8;
const double PI=acos(-1.0);
const int N=1e5+100;

ll ans,n,k,a[6]={1,0,1,2,9};
ll C(int n, int m){
    ll ret=1;
    for(int i=0; i<m; ++i){
        ret*=n-i;
    }
    for(int i=1; i<=m; ++i) ret/=i;
    return ret;
}
int main(){
    cin>>n>>k;
    for(int i=0; i<=k; ++i){
        ans+=C(n, i) * a[i];
    }
    cout<<ans<<endl;
    return 0;
}

E Maximum Subsequence

题解在这里