给定数列：1121231234...
求：某一位对应的数值
打表+二分
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#include<cstdio>
#include<cstring>
#include<cmath>
#define MAXN 111111
#define P 31268
#define N 2147483647
using namespace std;int a[10];
long long s[MAXN],sum[MAXN];int cal(int x)
{
return (int)log10(x)+1;
}void init()
{
int i=1;
long long cur=0;
while(cur<N)
{
s[i]=s[i-1]+cal(i);
cur=sum[i]=sum[i-1]+s[i];
i++;
}
}int find(long long x)
{
int l=1,r=P;
while(l<=r)
{
int m=(l+r)>>1;
if(sum[m]>x)r=m-1;
else if(sum[m]==x)return m-1;
else l=m+1;
}
return l-1;
}int find1(long long x)
{
int l=1,r=P;
while(l<=r)
{
int m=(l+r)>>1;
if(s[m]>x)r=m-1;
else if(s[m]==x)return m-1;
else l=m+1;
}
return l-1;
}int main()
{
//freopen("in.txt","r",stdin);init();
int t;
scanf("%d",&t);while(t--)
{
long long n;
scanf("%lld",&n);int p=find(n);
n-=sum[p];p=find1(n);
n-=s[p];p++;
int tot=0;
while(p)
{
a[++tot]=p%10;
p/=10;
}
int ans=a[tot+1-n];
printf("%d\n",ans);
}
return 0;
}
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