TBYqP3 - Online C++ Compiler & Debugging Tool

#include "bits/stdc++.h"
using namespace std;
#define fastio ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL);
#define vint vector<int>
#define int long long
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define cinv(T) for(auto& i : T) cin>>i;
#define nl '\n'
#define cy cout<<"YES\n"
#define cn cout<<"NO\n"
int dx[8] = {0, 0, 1, 1, 1, -1, -1, -1};
int dy[8] = {1, -1, 0, 1, -1, 0, 1, -1};


void solve() {
    int x, y, n; cin>>x>>y>>n;

    int a, b, bn = 1e9, bd = 1;

    for (int i = 1; i <= n; i++) { //try every possible denominator b
        int t = (x * i)/y; //we want a/b =~ x/y; thus, a =~ x*b/y (floor), so a + 1 also valid
        for (int j = t; j <= t + 1; j++) {
            // x/y - a/b = (x * b - a * y) / (y * b) = num / den
            int num = abs(x * i - j * y), den = y * i;

            //num/den -> value to be minimized
            if (num * 1.0 / den < bn * 1.0 / bd)
              b = i, a = j, bn = num, bd = den;

            if (num * 1.0 / den == bn * 1.0/ bd)
                if (i < b or (i == b and j < a))
                    b = i, a = j, bn = num, bd = den;

        }
    }

    cout<<a<<"/"<<b<<nl;
}

int32_t main() {
    fastio
    int t = 1; //cin>>t;
    while (t--) solve();
    return 0;
}