find num of common friends between users

main.go

package main

import (
	"fmt"

	"github.com/davecgh/go-spew/spew"
)

type adjList []int

// find num of common friends between 1 and other user
func main() {
	var adjLists = []adjList{
		[]int{}, // index from 1
		[]int{2, 3, 4},
		[]int{1, 3, 5},
		[]int{1, 2, 4, 5, 6, 7},
		[]int{1, 3},
		[]int{2, 3},
		[]int{3},
		[]int{3},
	}
	// spew.Dump(adjLists)

	var df [][]int
	// 1. map: omit possible pair
	for i := 1; i <= 7; i++ {
		al := adjLists[i]
		for j := 0; j < len(al)-1; j++ {
			for k := j + 1; k < len(al); k++ {
				df = append(df, []int{al[j], al[k]})
			}
		}
	}
	spew.Dump(df)
	fmt.Println("==========================")

	// 2. filter i = 1
	var filteredDf [][]int
	var filter = 1
	for _, row := range df {
		if row[0] == filter || row[1] == filter {
			filteredDf = append(filteredDf, row)
		}
	}

	spew.Dump(filteredDf)
	fmt.Println("==========================")

	// 3. group
	m := make(map[string]int)
	for _, row := range filteredDf {
		m[fmt.Sprintf("(%d, %d)", row[0], row[1])]++
	}

	for k, v := range m {
		fmt.Printf("%s: %d\n", k, v)
	}
}