POJ 1930 - Dead Fraction（数学）

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题目：

http://poj.org/problem?id=1930

题目：

将无限循环小数转化成分数，但是循环节不确定，要求出分母最小的那个分数。

思路：

百度知道了无限循环小数转化成分数的方法。详见笔记=。=

CODE:

#include <iostream>#include <cstdio>#include <cstring>#include <cmath>using namespace std;typedef long long ll;char s[10];ll gcd(ll a, ll b){    return b == 0? a: gcd(b, a%b);}int main(){//freopen("in", "r", stdin);    while(~scanf("%s", s)) {        int len = strlen(s);        if(s[0] == '0' && len == 1) break;        ll sum = 0;        len = 0;        for(int i = 2; s[i] != '.'; ++i) {            sum = sum * 10 + s[i]-'0';            len++;        }        //printf("%lld\n", sum);        ll num = sum, t = 1, up, ud;        ll on, down;        on = down = 1<<30;        for(int i = 1; i <= len; ++i) {            num /= 10;            t *= 10;            up = sum - num;            ud = (ll)pow(10.0, len - i) * (t - 1);            ll g = gcd(ud, up);            if((ud / g) < down) {                on = up/g;                down = ud/g;            }        }        printf("%I64d/%I64d\n", on, down);    }    return 0;}

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