题解 | 无限长正整数排列字符串

#include<bits/stdc++.h>
using namespace std;
char num[10]={'0','1','2','3','4','5','6','7','8','9'};string s[1111];string S;int n=0;int wei[111];
int main(){
    cin>>n;
    for (int i=1;i<=1000;++i) {
        int k=0,j=i;
    while (j) {
    ++k;wei[k]=j%10;j/=10;
    }
    for (;k>0;--k) {
    s[i]+=num[wei[k]];
    }
    }
    for (int i=1;i<=1000;++i) {
    S+=s[i];
    }
    cout<<S[n-1];
    return 0;
}