难点主要在分式的通分上面，转化成求最大公因数的问题。
#include <iostream> #include <climits> #include <map> using namespace std; struct Rational { long int fra; long int dec; }; Rational r1, r2; int pos = 1; int gcd(long int a, long int b) { if (b == 0) return a; else return gcd(b, a%b); } void printFra(long int fra, long int dec) { long int d = LONG_MAX; //有理化 if ((fra > dec || -fra > dec) && fra % dec != 0) { d = fra / dec; fra > 0 ? fra = fra : fra = -fra; fra = fra % dec; } else if (fra == 0 || (fra >= dec || -fra >= dec) && fra % dec == 0){ if(fra < 0 ) printf("(%ld)", fra / dec); else printf("%ld", fra / dec); return; } //通分 int tfra = fra; if (fra < 0) { tfra = -fra; } int factor = gcd(tfra, dec); fra /= factor; dec /= factor; //输出 if (d != LONG_MAX) { if (d < 0) { cout << "(" << d << " " << fra << "/" << dec << ")"; } else cout << d << " " << fra << "/" << dec ; } else { if (fra < 0) cout << "(" << fra << "/" << dec << ")"; else cout << fra << "/" << dec ; } } int main() { cin >> r1.fra; cin.get(); cin >> r1.dec; cin >> r2.fra; cin.get(); cin >> r2.dec; Rational a; //加法 printFra(r1.fra, r1.dec); cout << " + "; printFra(r2.fra, r2.dec); cout << " = "; a.fra = r1.fra * r2.dec + r2.fra * r1.dec; a.dec = r1.dec * r2.dec; printFra(a.fra, a.dec); cout << endl; //减法 printFra(r1.fra, r1.dec); cout << " - "; printFra(r2.fra, r2.dec); cout << " = "; a.fra = r1.fra * r2.dec - r2.fra * r1.dec; a.dec = r1.dec * r2.dec; printFra(a.fra, a.dec); cout << endl; //乘法 printFra(r1.fra, r1.dec); cout << " * "; printFra(r2.fra, r2.dec); cout << " = "; a.fra = r1.fra * r2.fra; a.dec = r1.dec * r2.dec; printFra(a.fra, a.dec); cout << endl; //除法 printFra(r1.fra, r1.dec); cout << " / "; printFra(r2.fra, r2.dec); cout << " = "; if (r2.fra == 0) { cout << "Inf" << endl; } else { if (r2.fra < 0) { r2.dec = -r2.dec; r2.fra = -r2.fra; } a.fra = r1.fra * r2.dec; a.dec = r1.dec * r2.fra; printFra(a.fra, a.dec); cout << endl; } return 0; }