[IOI2005]mea
IOI
读完题,感觉这个题并不是很难,那我是不是可以去IOI了:
最先考虑暴力,发现完全行不通,所以,我们考虑其他方法。突然发现:其实在确定 \(s_1\) 的时候,整个序列就可以确定了,所以我们考虑对 \(s_1\) 进行操作
通过题目中给出的条件,容易发现这个值与奇偶性有关系,所以 code:
注意在答案为负的情况下判 0
#include<iostream>
#include<cstdlib>
#include<cstdio>
#include<cmath>
#include<cstring>
#define int long long
using namespace std;
namespace xin_io
{
inline int get()
{
int s = 0,f = 1;
register char ch = getchar();
while(!isdigit(ch))
{
if(ch == '-') f = -1;
ch = getchar();
}
while(isdigit(ch))
{
s = s* 10 + ch - '0';
ch = getchar();
}
return s * f;
}
inline void openfile()
{freopen("t.txt","r",stdin);}
inline void outfile()
{freopen("o.txt","w",stdout);}
}
using xin_io::get; using xin_io::openfile; using xin_io::outfile;
namespace xin
{
int mx = 1ll<<60ll,mn = -mx;
int now,i,x,y,n;
inline short main()
{
n = get();
for (i = 1; i <= n; ++i, y = x)
{
x = get();
if (i & 1) now += x - y,mx = min(mx, now);
else now += y - x,mn = max(mn,now);
}
printf("%lld\n", mx < mn ? 0 : mx - mn + 1);
return 0;
}
}
signed main() {return xin::main();}