Codeforces Round #270 A B C
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ADesign Tutorial: Learn from Math
素数筛
#include<bits/stdc++.h> using namespace std; const int N = 1e6 + 100; int a[N]=0; int main() int n; cin >> n; a[1] = 1; for(int i = 2; i*i <= n; i++) if(a[i] == 0) for(int j = i*i; j <= n; j += i) a[j] = 1; for(int i = 2; i <= n; i++) if(a[i] && a[n-i]) cout << i << " " << n - i <<"\n"; return 0; return 0;
BDesign Tutorial: Learn from Life
贪心,从大到小,一次取k个,统计每次的楼层最高
#include<bits/stdc++.h> using namespace std; const int N = 2e3; int n, k; int a[N]; int main() cin >> n >> k; for(int i = 0; i < n; i++) cin >> a[i]; sort(a, a + n); int sum = 0; for(int i = n-1; i >= 0 ; i-=k) sum += (a[i] - 1) * 2; cout << sum << "\n"; return 0;
CDesign Tutorial: Make It Nondeterministic
模拟
#include<bits/stdc++.h> using namespace std; const int N = 1e5 + 100; int n; char s1[N][60]; char s2[N][60]; int a[N]; int main() cin >> n; for(int i = 1; i <= n; i++) cin >> s1[i] >> s2[i]; for(int i = 0; i < n; i++) cin >> a[i]; int p=3;//可以选任意一个为handle for(int i = 0; i < n-1; i++) bool b1=strcmp(s1[a[i]], s1[a[i+1]]) == -1; bool b2=strcmp(s2[a[i]], s1[a[i+1]]) == -1; bool b3=strcmp(s1[a[i]], s2[a[i+1]]) == -1; bool b4=strcmp(s2[a[i]], s2[a[i+1]]) == -1; if(p==3) if((b1|| b2) && (b3 || b4)); else if(b1 || b2) p=1;//只能选第一个为handle else if(b3 || b4) p=2;//只能选第二个为handle else cout<< "NO\n"; return 0; else if(p == 2) if(b2 && b4) p=3; else if(b2) p=1; else if(b4) p=2; else cout<< "NO\n"; return 0; else if( p== 1) if(b1 && b3) p=3; else if(b1) p=1; else if(b3) p=2; else cout<< "NO\n"; return 0; cout << "YES\n"; return 0;
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