HDU 1597: Find the nth Digit

Find the nth Digit Time Limit: 1000/1000 MS (Java/others) memory limit: 32768/32768 K (Java/Others)
Total submission (s): 8351 accepted submission (s): 2381


Problem description hypothesis:
S1 = 1
S2 = 12
S3. = 123
S4 = 1234
.........
S9 = 123456789
S10 = 1234567891
S11= 12345678912
............
S18= 123456789123456789
..................
Now we connect all strings
S = 1121231234 ...... 123456789123456789112345678912 .........
Can you tell me the nth number in the S string?
 
The input is a number K, which indicates K queries.
Each row in the next K Rows has an integer N (1 <=n <2 ^ 31 ).
For each n, output the nth number in S.
 
Sample Input

61234510

 
Sample output

112124

#include<cstdio>#include<string>#include<cmath>#include<cstring>#include<cctype>#include<cstdlib>#include<vector>#include<set>#include<map>#include<stack>#include<queue>#include<list>#include<algorithm>#include<iostream>#include<sstream>using namespace std;int main(){    int cas;    int n;    int sum;    scanf("%d", &cas);    while( cas-- )    {        scanf("%d", &n);        sum = 0;        for(int i=1; ; i++)        {            sum += i;            if( sum >= n )            {                sum -= i;                break;            }        }        int ans = n - sum;        if( ans % 9 == 0 ) printf("9\n");        else printf("%d\n", ans%9);    }    return 0;}