Codeforces_845
A.排序,比较中间两个大小。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include<bits/stdc++.h> using namespace std; int n,a[205]; int main() { ios::sync_with_stdio(0); cin >> n; for(int i = 1;i <= 2*n;i++) cin >> a[i]; sort(a+1,a+1+n*2); reverse(a+1,a+1+n*2); if(a[n] > a[n+1]) cout << "YES" << endl; else cout << "NO" << endl; return 0; }
B.优先改变价值大的位置。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include<bits/stdc++.h> using namespace std; int n,sub[6],add[6]; string s; int main() { ios::sync_with_stdio(0); cin >> s; int sum1 = 0,sum2 = 0; for(int i = 0;i < 3;i++) { sum1 += s[i]-'0'; sub[i] = s[i]-'0'; add[i] = '9'-s[i]; } for(int i = 3;i < 6;i++) { sum2 += s[i]-'0'; sub[i] = s[i]-'0'; add[i] = '9'-s[i]; } if(sum1 > sum2) { int t = sum1-sum2; int a[6]; for(int i = 0;i < 3;i++) a[i] = sub[i]; for(int i = 3;i < 6;i++) a[i] = add[i]; sort(a,a+6); reverse(a,a+6); for(int i = 0;i < 6;i++) { t -= a[i]; if(t <= 0) { cout << i+1 << endl; return 0; } } } else if(sum2 > sum1) { int t = sum2-sum1; int a[6]; for(int i = 0;i < 3;i++) a[i] = add[i]; for(int i = 3;i < 6;i++) a[i] = sub[i]; sort(a,a+6); reverse(a,a+6); for(int i = 0;i < 6;i++) { t -= a[i]; if(t <= 0) { cout << i+1 << endl; return 0; } } } else cout << 0 << endl; return 0; }
C.按l排序,优先队列模拟,处理出最小需要的TV数量。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include<bits/stdc++.h> using namespace std; int n; struct xx { int l,r; friend bool operator<(xx a,xx b) { return a.l < b.l; } }a[200005]; int main() { ios::sync_with_stdio(0); cin >> n; for(int i = 1;i <= n;i++) cin >> a[i].l >> a[i].r; sort(a+1,a+1+n); int ans = 0; priority_queue< int,vector<int>,greater<int> > q; for(int i = 1;i <= n;i++) { if(q.empty() || a[i].l <= q.top()) { ans++; q.push(a[i].r); } else { q.pop(); q.push(a[i].r); } } if(ans > 2) cout << "NO" << endl; else cout << "YES" << endl; return 0; }
D.栈模拟。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include<bits/stdc++.h> using namespace std; int n; int main() { ios::sync_with_stdio(0); cin >> n; stack<int> s; int ans = 0,now,cntover = 0; while(n--) { int x,y; cin >> x; if(x == 1) cin >> now; else if(x == 2) { ans += cntover; cntover = 0; } else if(x == 3) { cin >> y; s.push(y); } else if(x == 4) cntover = 0; else if(x == 5) { while(!s.empty()) s.pop(); } else cntover++; while(!s.empty() && now > s.top()) { ans++; s.pop(); } } cout << ans << endl; return 0; }
G.dfs,每遇到环可以存起来,最后更新答案。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include<bits/stdc++.h> using namespace std; int n,m,a[100005],vis[100005] = {0}; struct xx { int to,w; xx(int a,int b):to(a),w(b){}; }; vector<xx> v[100005]; vector<int> vv; void add(int x) { for(int i = 0;i < vv.size();i++) x = min(x,x^vv[i]); if(x) vv.push_back(x); } void dfs(int now,int val) { vis[now] = 1; a[now] = val; for(int i = 0;i < v[now].size();i++) { int t = v[now][i].to,w = v[now][i].w; if(vis[t]) add(val^w^a[t]); else dfs(t,w^val); } } int main() { ios::sync_with_stdio(0); cin >> n >> m; while(m--) { int x,y,z; cin >> x >> y >> z; v[x].push_back(xx(y,z)); v[y].push_back(xx(x,z)); } dfs(1,0); for(int i = 0;i < vv.size();i++) a[n] = min(a[n],a[n]^vv[i]); cout << a[n] << endl; return 0; }