学步园

题目链接：uva 474 - Heads / Tails Probability

题目大意：给定n，求12−n的科学计数法。

解题思路：n不大，递推一遍，维护小数和指数部分即可。

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
const int maxn = 1e6;

int k[maxn+5];
double arr[maxn+5];

void init (int n) {
    arr[1] = 5;
    k[1] = 1;
    for (int i = 2; i <= n; i++) {
        arr[i] = 0.5 * arr[i-1];
        k[i] = k[i-1];

        while (arr[i] < 1.0) {
            arr[i] *= 10;
            k[i]++;
        }
    }
}

int main () {
    int n;
    init(maxn);
    while (scanf("%d", &n) == 1) {
        printf("2^-%d = %.3lfe-%d\n", n, arr[n], k[n]);
    }
    return 0;
}