联赛模拟测试9 A. 嚎叫响彻在贪婪的厂房

题目描述

分析

一个序列是等差数列且公差不为1的条件就是各项差的绝对值的(gcd!=1)
从前往后依次扫即可
一定要判重

代码

#include<cstdio>
#include<algorithm>
#include<iostream>
#include<cmath>
#include<map>
inline int read(){
	int x=0,fh=1;
	char ch=getchar();
	while(ch<'0' || ch>'9'){
		if(ch=='-') fh=-1;
		ch=getchar();
	}
	while(ch>='0' && ch<='9'){
		x=(x<<1)+(x<<3)+(ch^48);
		ch=getchar();
	}
	return x*fh;
}
const int maxn=1e6+5;
int gcd(int aa,int bb){
	if(bb==0) return aa;
	return gcd(bb,aa%bb);
}
int n,a[maxn];
std::map<int,int> vis;
int main(){
	freopen("factory.in","r",stdin);
	freopen("factory.out","w",stdout);
	n=read();
	for(int i=1;i<=n;i++){
		a[i]=read();
	}
	int cnt=0,now,cs;
	for(int i=1;i<=n;i++){
		cnt++;
		if(i==n) break;
		now=std::abs(a[i]-a[i+1]);
		vis[a[i]]=vis[a[i+1]]=cnt;
		if(now<=1) continue;
		i++;
		while(1){
			if(vis[a[i+1]]==cnt) break;
			vis[a[i+1]]=cnt;
			cs=std::abs(a[i]-a[i+1]);
			if(cs<=1) break;
			now=gcd(now,cs);
			if(now<=1) break;
			i++;
		}
	}
	printf("%d
",cnt);
	return 0;
}