Educational Codeforces Round 79做题记录

Educational Codeforces Round 79做题记录

这套题感觉出的不咋滴，第四题和第五题难度差了1000分！！！

前四题都还简单，第五题就31人做出……我算了……

懒得写题解了，做个记录吧（这就是偷懒的理由？？？）

比赛传送门

A.New Year Garland

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>
#define rep(x, l, r) for(int x = l; x <= r; x++)
#define repd(x, r, l) for(int x = r; x >= l; x--)
#define clr(x, y) memset(x, y, sizeof(x))
#define all(x) x.begin(), x.end()
#define pb push_back
#define mp make_pair
#define MAXN
#define fi first
#define se second
#define SZ(x) ((int)x.size())
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;
const int INF = 1 << 30;
const int p = 1000000009;
int lowbit(int x){ return x & (-x);}
int fast_power(int a, int b){ int x; for(x = 1; b; b >>= 1){ if(b & 1) x = 1ll * x * a % p; a = 1ll * a * a % p;} return x % p;}

int main(){
    int t;
    scanf("%d", &t);
    while(t--){
        int a, b, c;
        scanf("%d%d%d", &a, &b, &c);
        if(a < b) swap(a, b);
        if(a < c) swap(a, c);
        if(a - 1 > b + c) puts("No");
        else puts("Yes");
    }
    return 0;
}

B.Verse For Santa

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>
#define rep(x, l, r) for(int x = l; x <= r; x++)
#define repd(x, r, l) for(int x = r; x >= l; x--)
#define clr(x, y) memset(x, y, sizeof(x))
#define all(x) x.begin(), x.end()
#define pb push_back
#define mp make_pair
#define MAXN 100005
#define fi first
#define se second
#define SZ(x) ((int)x.size())
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;
const int INF = 1 << 30;
const int p = 1000000009;
int lowbit(int x){ return x & (-x);}
int fast_power(int a, int b){ int x; for(x = 1; b; b >>= 1){ if(b & 1) x = 1ll * x * a % p; a = 1ll * a * a % p;} return x % p;}

int a[MAXN];

int main(){
    int t;
    scanf("%d", &t);
    rep(times, 1, t){
        int n, s;
        scanf("%d%d", &n, &s);
        rep(i, 1, n) scanf("%d", &a[i]);
        int sum = 0, maxx = 0, ans = 0;
        rep(i, 1, n){
            sum += a[i];
            if(a[i] > maxx){
                maxx = a[i];
                ans = i;
            }
            if(sum > s) break;
        }
        if(sum <= s) puts("0");
        else printf("%d
", ans);
    }
    return 0;
}

C.Stack of Presents

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>
#define rep(x, l, r) for(int x = l; x <= r; x++)
#define repd(x, r, l) for(int x = r; x >= l; x--)
#define clr(x, y) memset(x, y, sizeof(x))
#define all(x) x.begin(), x.end()
#define pb push_back
#define mp make_pair
#define MAXN
#define fi first
#define se second
#define SZ(x) ((int)x.size())
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;
const int INF = 1 << 30;
const int p = 1000000009;
int lowbit(int x){ return x & (-x);}
int fast_power(int a, int b){ int x; for(x = 1; b; b >>= 1){ if(b & 1) x = 1ll * x * a % p; a = 1ll * a * a % p;} return x % p;}

int main(){
    int t;
    scanf("%d", &t);
    rep(times, 1, t){
        int n;
        scanf("%d", &n);
        ll s1 = 0, s2 = 0;
        rep(i, 1, n){
            ll x;
            scanf("%lld", &x);
            s1 += x;
            s2 ^= x;
        }
        s2 <<= 1;
        ll ans = 0;
        for(int i = 0; s1 != s2; i++){
            if((s1 & 1) ^ (s2 & 1)){
                s1 += 1;
                s2 ^= 2;
                ans += 1ll << i;
            }
            s1 >>= 1;
            s2 >>= 1;
        }
        printf("1
%lld
", ans);
    }
    return 0;
}

D.Santa's Bot

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>
#define rep(x, l, r) for(int x = l; x <= r; x++)
#define repd(x, r, l) for(int x = r; x >= l; x--)
#define clr(x, y) memset(x, y, sizeof(x))
#define all(x) x.begin(), x.end()
#define pb push_back
#define mp make_pair
#define MAXN 1000005
#define fi first
#define se second
#define SZ(x) ((int)x.size())
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;
const int INF = 1 << 30;
const int p = 998244353;
int lowbit(int x){ return x & (-x);}
int fast_power(int a, int b){ int x; for(x = 1; b; b >>= 1){ if(b & 1) x = 1ll * x * a % p; a = 1ll * a * a % p;} return x % p;}

vi a[MAXN];
int inv[MAXN], id[MAXN], sum[MAXN];

int main(){
    int n;
    scanf("%d", &n);
    inv[1] = 1;
    rep(i, 2, 1000000) inv[i] = 1ll * (p - p / i) * inv[p % i] % p;
    rep(i, 1, n){
        int k;
        scanf("%d", &k);
        rep(j, 1, k){
            int x;
            scanf("%d", &x);
            a[i].pb(x);
            if(id[x] != i){
                sum[x]++;
                id[x] = i;
            }
        }
    }
    int ans = 0;
    rep(i, 1, n){
        rep(j, 0, SZ(a[i]) - 1){
            ans = (ans + 1ll * sum[a[i][j]] * inv[n] % p * inv[n] % p * inv[SZ(a[i])] % p) % p;
        }
    }
    printf("%d
", ans);
    return 0;
}