思路:最大值肯定存在相鄰的數之間,用線段樹維護區間最大值(用C++14會內存超限)
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <set>
#include<iostream>
#include<vector>
using namespace std;
typedef long long ll;
#define SIS std::ios::sync_with_stdio(false)
#define space putchar(' ')
#define enter putchar('\n')
#define lson root<<1
#define rson root<<1|1
typedef pair<int,int> PII;
const int mod=1e4+7;
const int N=2e5+10;
const int inf=0x7f7f7f7f;
ll gcd(ll a,ll b)
{
return b==0?a:gcd(b,a%b);
}
ll lcm(ll a,ll b)
{
return a*(b/gcd(a,b));
}
template <class T>
void read(T &x)
{
char c;
bool op = 0;
while(c = getchar(), c < '0' || c > '9')
if(c == '-')
op = 1;
x = c - '0';
while(c = getchar(), c >= '0' && c <= '9')
x = x * 10 + c - '0';
if(op)
x = -x;
}
template <class T>
void write(T x)
{
if(x < 0)
x = -x, putchar('-');
if(x >= 10)
write(x / 10);
putchar('0' + x % 10);
}
struct node
{
int l,r;
int maxx;
}tr[N<<2];
int a[N];
void push_up(int root)
{
tr[root].maxx=max(tr[lson].maxx,tr[rson].maxx);
return ;
}
void build(int l,int r,int root)
{
tr[root].l=l;tr[root].r=r;
if(l==r)
{
tr[root].maxx=a[l+1]-a[l];
return ;
}
int mid=l+r>>1;
build(l,mid,lson);
build(mid+1,r,rson);
push_up(root);
return ;
}
void update(int root,int x,int k)
{
if(tr[root].l==x&&tr[root].r==x)
{
tr[root].maxx=k;
return ;
}
int mid=tr[root].l+tr[root].r>>1;
if(mid>=x)
update(lson,x,k);
else
update(rson,x,k);
push_up(root);
return ;
}
int main()
{
int n;
while(~scanf("%d",&n))
{
for(int i=1;i<=n;i++)
read(a[i]);
int m;
read(m);
build(1,n-1,1);
while(m--)
{
int x,k;
read(x),read(k);
a[x]=k;
if(x!=n)update(1,x,a[x+1]-a[x]);
if(x!=1)update(1,x-1,a[x]-a[x-1]);
int ans=tr[1].maxx;
double res=(double)ans;
printf("%.2f\n",res);
}
}
return 0;
}