#include<iostream>
using namespace std;
double a,b,aa,bb,l;
int gcd(int a,int b){return b==0?a:gcd(b,a%b);}
int main()
{
cin>>a>>b>>l;
double ans=a/b;
double ans2=0.0000;
double ans3=1000000.00;
for(double i=1.0;i<=l;i++)
{
for(double j=1.0;j<=l;j++)
{

ans2=(double)i/j;
double ans4=ans2-ans;
if(ans4>=0&&gcd((int)i,(int)j)==1&&ans4<=ans3){ans3=ans4;aa=i;bb=j;}
}
}
cout<<aa<<" "<<bb<<endl;
return 0;
}

var a,b,l,i,j,min_a,min_b:longint; min:real;
function g(a,b:longint):longint;
begin
if a<b then begin a:=a+b; b:=a-b; a:=a-b; end;
if a mod b=0 then exit(b);
exit(g(b,a mod b));
end;

begin
read(a,b,l); min:=maxlongint; min_a:=0; min_b:=0;
if a=b then writeln('1 1')
else
begin
for i:=1 to l do
for j:=1 to l do
if (i/j>=a/b) and (g(i,j)=1) and (i/j-a/b<min) then
begin min:=i/j-a/b; min_a:=i; min_b:=j; end;
writeln(min_a,' ',min_b);
end;
end.

双指针扫描

#include <stdio.h>
int main(){
double A,B,max;
double pointerA=1,pointerB=1,ansA=10000,ansB=1;
scanf("%lf%lf%lf",&A,&B,&max);
while(1){
if(pointerA/pointerB>=A/B && ansA/ansB>pointerA/pointerB)
ansA=pointerA,ansB=pointerB;
if(pointerA/pointerB>A/B){
if(pointerB<max)
pointerB++;
else
break;
}else if(pointerA/pointerB<A/B){
if(pointerA<max)
pointerA++;
else
break;
}else{
break;
}
}
printf("%.0lf %.0lf\n",ansA,ansB);
return 0;
}

#include<cstdio>
int a,b,l,ansx,ansy;
double min=123456789.0,s,tmp;
int gcd(int a,int b) {return b?gcd(b,a%b):a;}
int main()
{
scanf("%d%d%d",&a,&b,&l),s=(double)a/(double)b;
for(int i=1;i<=l;i++)
for(int j=1;j<=l;j++)
gcd(i,j)==1&&(tmp=(double)i/double(j))>=s&&tmp<=min?(ansx=i,ansy=j,min=tmp):1;
printf("%d %d\n",ansx,ansy);
return 0;
}

var
n,m,i,j,x,y,l:longint;
function gcd(m,n:longint):longint;
begin
if m mod n=0 then exit(n)
else gcd:=gcd(n,m mod n);
end;
begin
readln(m,n,l);
x:=maxlongint;y:=1;
for i:=1 to l do
for j:=1 to l do
if (gcd(i,j)=1)and(i/j-m/n<x/y-m/n)and(i/j>=m/n) then
begin
x:=i;
y:=j;
end;
writeln(x,' ',y);
end.

坑爹啊 居然不是算误差 而是【正】误差 60分都是错这了

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;
int gcd(int x,int y){
if(y != 0){
return gcd(y, x%y);
}else{
return x;
}

}

float a,b;
int l;
float mi = 0x3f3f3f3f;
int a1,b1;
int main(){
cin>>a>>b>>l;
float tempi, tempj;
for(int i = 1; i <= l; i++){
for(int j = 1; j <= l; j++){
tempi = i;
tempj = j;
if(gcd(i,j) == 1){
if(tempi/tempj >= a/b){
if(tempi/tempj - a/b < mi){
mi = tempi/tempj - a/b;
a1 = i;
b1 = j;
}
}
}
}
}
printf("%d %d", a1, b1);

return 0;
}

#include <iostream>
#include <cstdio>
using namespace std;
int gcd(int a, int b)
{
    if(a == 0)
    {
        return b;
    }

    if(b == 0)
    {
        return a;
    }

    if(a & 1 == 0 && b & 1 == 0)
    {
        return gcd(a >> 1, b >> 1) << 1;
    }
    else
        if(a & 1 == 0)
        {
            return gcd(a >> 1, b);
        }
        else
            if(b & 1 == 0)
            {
                return gcd(a, b >> 1);
            }
            else
            {
                return gcd(a - b >= 0 ? a - b : b - a, min(a, b));
            }
}
int a, b, t, x, y, l;
double _min = 3838438;
int main()
{
    ios::sync_with_stdio(false);
    cin >> a >> b >> l;
    t = gcd(a, b);

    while(t > 1)
    {
        a /= t;
        b /= t;
        t = gcd(a, b);
    }

    if(a > l || b > l)
        for(int i = 1; i <= l; i++)
            for(int j = 1; j <= l; j++)
            {
                if(gcd(i, j) == 1 && i * 1.0 / j * 1.0 > a * 1.0 / b * 1.0 && i * 1.0 / j * 1.0 < _min)
                {
                    x = i;
                    y = j;
                    _min = i * 1.0 / j * 1.0;
                }
            }
    else
    {
        x = a;
        y = b;
    }

    cout << x << ' ' << y;
}

少了一句判断i/j>=a/b就WA了4个点。。