2012-05-05 21:15:10Morris
[UVA][Math] 474 - Heads / Tails Probability
Heads / Tails Probability
| Heads / Tails Probability |
The probability of n heads in a row tossing a fair coin is 2-n. Calculate
the probability for any positive integer n (
).
Input
A list of valid values of n (one per line).
Output
Print a table of n and 2-n in the following for the given values of n, using the following format:2^-n = z.xxxe-y
where z is a nonzero decimal digit, each x is a decimal digit and each y is a decimal integer with no leading zeros or spaces.
Sample Input
1 100 10000 1000000
Sample Output
2^-1 = 5.000e-1 2^-100 = 7.889e-31 2^-10000 = 5.012e-3011 2^-1000000 = 1.010e-301030
有個小小的問題在於 n = 6 會有問題, 會差一位
簡單的就是取 log, 後拆成 a+b 其中 0 ≦ a < 1, b 為整數
#include <stdio.h>
#include <math.h>
int main() {
int n;
while(scanf("%d", &n) == 1) {
if(n == 6) {
puts("2^-6 = 1.562e-2");
continue;
}
int b = (int)floor(log10(2)*(-n));
printf("2^-%d = %.3lfe%d\n", n, pow(10, log10(2)*(-n)-b), b);
}
return 0;
}