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import (
 "fmt"
 "sync"
)

var (
 parts = 4
)

func main() {
 numbers := []int{3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5} // Example array
 totalSum := concurrentSum(numbers, parts)         // Divide the array into 4 parts for summing
 fmt.Println("Total Sum:", totalSum)
}

// sumPart sums a part of the array and sends the result to a channel.
func sumPart(workerId int, nums []int, result chan<- int, wg *sync.WaitGroup) {
 defer wg.Done() // Ensure the WaitGroup counter decrements on function completion.
 sum := 0
 for _, num := range nums {
  sum += num
 }
 fmt.Printf("Worker %d calculated sum: %d\n", workerId, sum)
 result <- sum // Send the partial sum to the result channel.
}

// concurrentSum takes an array and the number of parts to divide it into,
// then sums the array elements using concurrent goroutines.
func concurrentSum(numbers []int, parts int) int {
 n := len(numbers)
 partSize := n / parts // Determine the size of each subarray
 fmt.Printf("Dividing the array of size %d into %d parts of size %d\n", n, 
  parts, partSize)
 results := make(chan int, parts) // Channel to collect results with a buffer size
 
var wg sync.WaitGroup
 // Fork step: Launch a goroutine for each part of the array
 for i := 0; i < parts; i++ {
  start := i * partSize
  end := start + partSize
  if i == parts-1 { // Ensure the last goroutine covers the remainder of the array
   end = n
  }
  wg.Add(1)
  go sumPart(i, numbers[start:end], results, &wg)
 }

 // Close the results channel once all goroutines are done
 go func() {
  wg.Wait()
  close(results)
 }()

 // Join step: Combine results
 totalSum := 0
 for sum := range results {
  fmt.Printf("Received partial sum: %d\n", sum)
  totalSum += sum
 }

 return totalSum
}