【HDOJ】1597 find the nth digit

二分。

 1 #include <stdio.h>
 2 #include <math.h>
 3 
 4 int main() {
 5     int case_n;
 6     double n, tmp, l, r;
 7     int m;
 8 
 9     scanf("%d", &case_n);
10 
11     while (case_n--) {
12         scanf("%lf", &n);
13         tmp = sqrt(n+n);
14         tmp = ceil(tmp);
15         l = (tmp*tmp-tmp)/2;
16         r = (tmp*tmp+tmp)/2;
17         while ( !(l<n && r>=n) ) {
18             --tmp;
19             l = (tmp*tmp-tmp)/2;
20             r = (tmp*tmp+tmp)/2;
21         }
22         m = (int)(n-l);
23         m %= 9;
24         if (m==0) m=9;
25         printf("%d\n", m);
26     }
27 
28     return 0;
29 }