Codeforces Round #172 (Div. 2)

意外的變藍了，才解了兩道 ，以爲要掉rating呢

最近好幾次CF都掛在精度上了，這次也是，B題又忘記用64位了 導致錯了幾次

A題

首字母大寫

#include <iostream>
#include<cstdio>
#include<cstring>
#include<stdlib.h>
using namespace std;
char str[1010];
int main()
{
    int i,j,k,n;
    cin>>str;
    if(str[0]>='a'&&str[0]<='z')
    str[0] = str[0]-32;
    puts(str);
    return 0;
}

 

B題 枚舉從1到N 注意一下精度

#include <iostream>
#include<cstdio>
#include<cstring>
#include<stdlib.h>
#include<algorithm>
#define INF 100000
using namespace std;
#define LL __int64
LL gcd(LL  a,LL b)
{
    return b==0? a:gcd(b,a%b);
}
void change(LL x,LL y)
{
    int i,j;
    LL  k = min(x,y);
    for(i = 2 ; i <= k ; i++)
    {
        while(x%i==0&&y%i==0)
        {
            x = x/i;
            y = y/i;
        }
        if(x<i||y<i)
        break;
    }
    printf("%I64d/%I64d\n",x,y);
}
int main()
{
    int i,j;
    LL k,n,x,y,d,t1,t2,a,yy;
    double s;
    cin>>x>>y>>n;
    if(y<=n)
    {
        change(x,y);
        return 0;
    }
    double mi = 10000000000;
    for(i = 1; i <= n ; i++)
    {
        k = y*i/gcd(y,i);
        LL kk = k/y*x;
        yy = k/i;
        if(abs(kk-kk/yy*yy)>abs(kk-(kk/yy+1)*yy))
        {
           a = kk/yy+1;
           d = abs(kk-(kk/yy+1)*yy);
        }
        else
        {
            a = kk/yy;
            d = abs(kk-(kk/yy)*yy);
        }
        s = d*INF*1.0/k;
        if(mi>s)
        {
            t1 = a;
            t2 = i;
            mi = s;
        }
    }
    change(t1,t2);
    return 0;
}