标签：printf getch bit 判断 getc 题意 分类 names closed
A - Circle of Students
题意：判断是否是1,2,3...n的排列或者n,n-1...2,1的排列
思路1：分类讨论，如果是递增的，ai-i的值固定，如果递减，ai+i的值固定
#include<bits/stdc++.h> #define rep(i,a,b) for(int i=a;i<=b;i++) #define dep(i,a,b) for(int i=b;i>=a;i--) using namespace std; #define ll long long const int N=3e5+5; const int mod = 998244353; int T,n,a[101010],flag; ll rd() { ll x=0,f=1;char ch=getchar(); while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();} while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();} return x*f; } int main() { T=rd(); while(T--) { n=rd(); flag=1; rep(i,1,n) a[i]=rd(); rep(i,2,n) { if((a[i]-a[1]+n)%n!=(i-1)) flag=0; } if(flag) { printf("YES\n"); continue; } flag=1; rep(i,2,n) { if((a[i]+i)%n!=(a[1]+1)%n) flag=0; } if(!flag) printf("NO\n"); else printf("YES\n"); } }
思路2：直接做
#include<bits/stdc++.h> #define rep(i,a,b) for(int i=a;i<=b;i++) #define dep(i,a,b) for(int i=b;i>=a;i--) using namespace std; #define ll long long const int N=3e5+5; const int mod = 998244353; int T,n,a[101010],flag; ll rd() { ll x=0,f=1;char ch=getchar(); while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();} while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();} return x*f; } int main() { T=rd(); while(T--) { n=rd(); flag=1; rep(i,1,n) a[i]=rd(); rep(i,2,n) { if(a[i]-1==a[i-1]) continue; else if(a[i]==1&& a[i-1]==n) continue; flag=0; } if(flag) { printf("YES\n"); continue; } flag=1; rep(i,2,n) { if(a[i]+1==a[i-1]) continue; else if(a[i]==n&& a[i-1]==1) continue; flag=0; } if(!flag) printf("NO\n"); else printf("YES\n"); } }
Codeforces Round #579 (Div. 3)
标签：printf getch bit 判断 getc 题意 分类 names closed
原文地址：https://www.cnblogs.com/The-Pines-of-Star/p/11355608.html
