2020牛客国庆集训派对day1

2020牛客国庆集训派对day1

A ABB

马拉夫算法

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
 int N=4e5+10;
int base=11;
int n;
char s[400005];
int main()
{
    
    
    scanf("%d%s", &n, s);
    ll h1=0, h2=0, t=1;
    int ans=0;
    for(int i=n-1; i>=0; i--) {
    
    
        h1=h1*base+s[i];
        h2=h2+s[i]*t; t*=base;
        if(h1==h2) ans=i;
    }
    printf("%d\n", ans);
    return 0;
}

#include <bits/stdc++.h>

#define int ll
//#pragma GCC optimize(2)
using namespace std;
typedef long long ll;
const int maxn = 4e5 + 10;

int n;
char p[maxn],s[maxn<<1];
int l[maxn<<1];

int manacher() {
    
    
    int cnt=0;
    s[cnt]='@';s[++cnt]='#';
    for (int i = 0; i <n; ++i)
        s[++cnt]=p[i],s[++cnt]='#';
    int mr=0,cen=0,ans=cnt;
    for (int i = 1; i <=cnt; ++i) {
    
    
        if (mr>=i) l[i]=min(l[2*cen-i],mr-i);
        else l[i]=1;
        while (s[i-l[i]]==s[i+l[i]]) l[i]++;
        if (mr<l[i]+i) mr=l[i]+i,cen=i;
        if (l[i]+i-1==cnt) ans=min(ans,(i-l[i]+1)/2);
    }
    return ans;
}

void solve() {
    
    
    cin>>n>>p;
    cout<<manacher();
}

signed main() {
    
    
    //ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int _ = 1;
    //cin >> _;
    while (_--) {
    
    
        solve();
    }
    return 0;
}

C Bob in Wonderland

#include <bits/stdc++.h>

#define int ll
#pragma GCC optimize(2)
using namespace std;
typedef long long ll;
const int maxn = 3e5 + 10;

int d[maxn];

void solve() {
    
    
    int n,ans=0;
    cin>>n;
    for(int i=0;i<n-1;i++){
    
    
        int u,v;
        cin>>u>>v;
        d[u]++,d[v]++;
    }
    for (int i = 0; i <=n; ++i) {
    
    
        if (d[i]>2) ans+=d[i]-2;
    }
    cout<<ans;
}

signed main() {
    
    
    //ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int _ = 1;
    //cin >> _;
    while (_--) {
    
    
        solve();
    }
    return 0;
}