CodeforcesCodeforces Round #491 (Div. 2) (Contest 991)
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题目
传送门:QWQ
A:A - If at first you don‘t succeed...
分析:
按照题意模拟
代码:
#include <bits/stdc++.h> using namespace std; int main(){ int a,b,c,n; scanf("%d%d%d%d",&a,&b,&c,&n); int ans=n-a-b+c; if(a<c || b<c) ans=-1; if(ans>0) printf("%d ",ans); else puts("-1"); }
B:B - Getting an A
分析:
显然把越小的改成5贡献越大。
代码:
#include <bits/stdc++.h> using namespace std; const int maxn=300; int a[maxn]; int main(){ int n;scanf("%d",&n); for(int i=1;i<=n;i++) scanf("%d",&a[i]); sort(a+1,a+1+n); int sum=0,ans=0;for(int i=1;i<=n;i++) sum+=a[i]; for(int i=1;i<=n;i++){ // cout<<(double)(sum*1.0/n)<<endl; if((double)(sum*1.0/n)>=4.5) break; int k=5-a[i]; ans++; sum+=k; } printf("%d ",ans); }
C:C - Candies
分析:
大力二分
代码:
#include <bits/stdc++.h> using namespace std; typedef long long ll; ll n; int ok(ll k){ ll sum=0,x=n; while(x>=0){ if(x>=k) sum+=k;else sum+=x; x=max(x-k,-1ll); x-=x/10; } // printf("---- %lld %lld ",k,sum); return sum>=(n+1)/2; } int main(){ cin>>n; ll l=0,r=n+5; while(l+1<r){ ll mid=l+r>>1; // cout<<l<<" "<<r<<endl; if(ok(mid)) r=mid; else l=mid; } cout<<r; }
D:D - Bishwock
分析:
按位从从左到右扫过去,能填进去就填进去
代码:
#include <bits/stdc++.h> using namespace std; const int maxn=200; char s[maxn], s2[maxn]; int main(){ scanf("%s%s",s+1,s2+1); int n=strlen(s+1); int ans=0; s[0]=‘X‘; s2[0]==‘X‘; for(int i=1;i<=n;i++){ if(s[i]==‘X‘) continue; if(s2[i]==‘0‘ && s2[i-1]==‘0‘){ s2[i]=‘X‘; s2[i-1]=‘X‘; s[i]=‘X‘; ans++; // printf("%d 1 ",i); continue; } if(s2[i]==‘0‘ && s2[i+1]==‘0‘){ s2[i]=‘X‘; s2[i+1]=‘X‘; s[i]=‘X‘; ans++; // printf("%d 2 ",i); continue; } if(s[i+1]==‘0‘ && s2[i]==‘0‘){ s2[i]=‘X‘; s[i+1]=‘X‘; s[i]=‘X‘; ans++; // printf("%d 3 ",i); continue; } if(s[i+1]==‘0‘ && s2[i+1]==‘0‘){ s2[i+1]=‘X‘; s[i+1]=‘X‘; s[i]=‘X‘; ans++; // printf("%d 3 ",i); continue; } } // printf("%s %s ",s+1,s2+1); printf("%d ",ans); }
E:E - Bus Number
分析:
https://blog.csdn.net/ZscDst/article/details/80835561
官方题解做法。。。。。
代码:
//copy from https://blog.csdn.net/ZscDst/article/details/80835561 #include<bits/stdc++.h> using namespace std; typedef long long ll; int a[15], vis[15]; ll fac[20]; set<string> s; void split(string x, int *a) { for (int i = 0; i < 10; i++) a[i] = 0; for (char i: x) a[i-‘0‘]++; } ll getcount()//去重全排列 { ll ans = fac[accumulate(a, a+10, 0)]; for (int i = 0; i < 10; i++) ans /= fac[a[i]]; return ans; } ll getans(string x) { split(x, a); for (int i = 0; i < 10; i++) if (vis[i] && !a[i]) return 0;//比原来少了i数字 sort(x.begin(), x.end()); if (s.count(x)) return 0;//x这种子集算过了 else s.insert(x); ll ans = getcount(); if (a[0]) { a[0]--; ans -= getcount(); }//减去前导0情况 return ans; } int main() { fac[0] = 1; for(int i = 1; i < 20; i++) fac[i] = fac[i-1]*i;//计算阶乘 string n; cin >> n; split(n, vis); int k = n.size(); ll ans = 0; for (int i = 1; i < (1<<k); i++)//二进制枚举 { string t; for (int j = 0; j < k; j++) if (i&(1<<j)) t += n[j]; ans += getans(t); } printf("%lld ",ans); return 0; }
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