CodeForces 48C D - The Race （Fraction，数学）

每个加油的站可以确定一个alpha的上下界，比如，第i次加油站a[i]，前面加了i次油，a[i]*10≤ alpha*i <(a[i]+1)*10。

取最大的下界，取最小的上界，看看两者之间的满足条件的下一个加油站是否唯一。

因为可以用分数，所有就没用double了

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a; }
struct Fra
{ll p,q;Fra(ll x = 0,ll y = 1):p(x),q(y){ normal(p,q); }void normal(ll &p,ll &q) { ll g = gcd(p,q); p/=g; q/=g; }Fra operator = (int x) {  p = x; q = 1; return *this; }Fra operator = (ll x) { p = x; q = 1; return *this; }Fra operator - () { return {-p,q}; }Fra operator + (Fra &r) {ll m,n;m = p*r.q+r.p*q;n = q*r.q;normal(m,n);return {m,n};}Fra operator += (Fra& r) { return *this = *this+r; }Fra operator - (Fra &r) { return (-r) + *this; }Fra operator -= (Fra &r) { return *this = *this-r; }Fra operator * (Fra &r) {ll m,n;m = p*r.p;n = q*r.q;normal(m,n);return {m,n};}Fra operator *= (Fra &r) { return (*this) = (*this)*r; }Fra operator /(Fra &r) { return Fra(r.q,r.p) * (*this); }Fra operator /=(Fra &r) { return (*this) = (*this)/r; }bool operator == (const Fra& r) const { return p*r.q == r.p*q; }bool operator < (const Fra& r) const { return  p*r.q < r.p*q; }void print() { normal(p,q); if(q<0)q = -q,p = -p; printf("%lld/%lld\n",p,q); }
};const int maxn = 1e3+5;const ll INF = 1e16;
int main()
{//freopen("in.txt","r",stdin);int n; scanf("%d",&n);Fra Low(0),High(INF);for(int i = 1; i <= n; i++){int t; scanf("%d",&t);Low = max(Fra(t*10,i),Low);High = min(Fra(t*10+10,i),High);}Low = Fra(n+1)*Low;High = Fra(n+1)*High;int u = (High.p-1)/High.q;int d = (Low.p)/Low.q;if(u/10 != d/10) {puts("not unique");}else {printf("unique\n%d",d/10);}return 0;
}

转载于:https://www.cnblogs.com/jerryRey/p/4783571.html

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