Added Pythagorean Triplet efficient method

Author: gokivego

MathAndStats/PythagoreanTriplets.go

@@ -5,13 +5,15 @@ Given an array find all the pythagorean triplets (a^2 + b^2 = c^2)
 package main
 
 import ("fmt"
+ "sort"
 )
 
 type triplet struct {
  a,b,c int
 }
 
 // This solution is O(n^3) in time complexity and space complexity is O(1)
+// For every combination of a,b,c we iterate to find the solution
 func PythagoreanTripletsBruteForce(array []int) *[]triplet {
  var tripletArray []triplet
  for i:=0;i<len(array);i++ {
@@ -28,10 +30,31 @@ func PythagoreanTripletsBruteForce(array []int) *[]triplet {
 
 // The Pythagorean triplet using a 3SUM approach
 // The time complexity of the solution is O(n^2) and Space complexity (1)
-
+func PythagoreanTriplets3Sum(array sort.IntSlice) *[]triplet {
+ array.Sort() // Sorted Array
+ var tripletArray []triplet
+ for k:=len(array)-1;k>1;k-- {
+ i := 0
+ j := k-1
+ for j!=i {
+ if (array[i]*array[i] + array[j]*array[j] - array[k]*array[k] > 0) {
+ j-- 
+ } else if (array[i]*array[i] + array[j]*array[j] - array[k]*array[k] < 0) {
+ i++
+ } else {
+ tripletArray = append(tripletArray,triplet{array[i],array[j],array[k]})
+ break
+ }
+ } 
+ }
+ return &tripletArray
+}
 
 func main() {
  array := []int{4,16,1,2,3,5,6,8,25,10}
- tripletArrayPtr := PythagoreanTripletsBruteForce(array)
- fmt.Println(*tripletArrayPtr)
+ var array1 sort.IntSlice = array //Using this type to do sorting 
+ tripletArrayPtr1 := PythagoreanTripletsBruteForce(array)
+ fmt.Println(*tripletArrayPtr1)
+ tripletArrayPtr2 := PythagoreanTriplets3Sum(array1)
+ fmt.Println(*tripletArrayPtr2)
 }