The challenge
You will have a list of rationals in the form:
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lst = [ [numer_1, denom_1] , ... , [numer_n, denom_n] ]
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where all numbers are positive integers. You have to produce their sum N / D in an irreducible form: this means that N and D have only 1 as a common divisor.
Return the result in the form: "N/D"
If the result is an integer (D evenly divides N) return: "n"
If the input list is empty, return: "0"
Examples:
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[ [1, 2], [1, 3], [1, 4] ] --> [13, 12]
1/2 + 1/3 + 1/4 = 13/12
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The solution in Golang
Option 1:
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package solution
import"fmt"
func SumFracts(arr[][]int) string {
a,b:= 0,1
for _,v:=range arr{
c,d:=v[0],v[1]
k:=gcd(b,d)
a,b=(a*d+b*c)/k,b*d/k
}
k:=gcd(a,b)
a,b=a/k,b/k
if b==1 {return fmt.Sprintf("%d",a)}
return fmt.Sprintf("%d/%d",a,b)
}
func gcd(a, b int) int {
for b != 0 {
a, b = b, a%b
}
return a
}
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Option 2:
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package solution
import "math/big"
func SumFracts(arr [][]int) string {
result := new(big.Rat).SetFloat64(0)
for _, v := range(arr) {
rat := big.NewRat(int64(v[0]), int64(v[1]))
result.Add(result, rat)
}
return result.RatString()
}
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Option 3:
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package solution
import "math/big"
func SumFracts(arr [][]int) string {
sum := big.NewRat(0,1)
for _, f := range arr {
sum.Add(sum, big.NewRat(int64(f[0]), int64(f[1])))
}
if sum.Denom().Cmp(big.NewInt(1)) == 0 {
return sum.Num().String()
}
return sum.String()
}
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Test cases to validate our solution
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package solution_test
import (
. "github.com/onsi/ginkgo"
. "github.com/onsi/gomega"
)
func dotest(arr [][]int, exp string) {
var ans = SumFracts(arr)
Expect(ans).To(Equal(exp))
}
var _ = Describe("Tests SumFracts", func() {
It("should handle basic cases", func() {
dotest([][]int{{1, 2}, {1, 3}, {1, 4}}, "13/12")
dotest([][]int{{1, 3}, {5, 3}}, "2")
})
})
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