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# yosu/celebrity.go

Last active February 3, 2016 05:01
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5.5 Celebrity Problem - Introduction to Algorithms by Udi Manber
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 package main import ( "bufio" "flag" "fmt" "os" "strconv" "strings" ) type Reader struct { *bufio.Scanner } func NewReader() *Reader { scanner := bufio.NewScanner(os.Stdin) return &Reader{scanner} } func (r *Reader) scanInt() int { r.Scan() n, _ := strconv.Atoi(r.Text()) return n } func (r *Reader) scanIntArray() []int { text := r.scanText() strs := strings.Split(text, " ") ints := make([]int, len(strs)) for i, v := range strs { ints[i], _ = strconv.Atoi(v) } return ints } func (r *Reader) scanText() string { r.Scan() return r.Text() } func main() { r := NewReader() n := r.scanInt() m := [][]int{} for i := 0; i < n; i++ { m = append(m, r.scanIntArray()) } var algorithm = flag.Int("algorithm", 1, "select algorithm type: 1 - simple, 2 - fine") flag.Parse() fmt.Fprintf(os.Stderr, "Algorithm: %d\n", *algorithm) celeb := findCelebrity(m, *algorithm) if celeb != -1 { fmt.Printf("%d\n", celeb+1) } else { fmt.Println("no celeb") } } func knownByAll(m [][]int, j int) bool { for i := 0; i < len(m); i++ { if m[i][j] == 0 && i != j { return false } } return true } func knowAny(m [][]int, i int) bool { for j := 0; j < len(m); j++ { if m[i][j] == 1 && i != j { return true } } return false } func findCandidate(m [][]int) int { i := 0 j := 1 next := 2 n := len(m) for next <= n { if m[i][j] == 1 { i = next } else { j = next } next = next + 1 } if i == n { return j } return i } func findCelebrity(m [][]int, algorithm int) int { if algorithm == 1 { return findCelebrity1(m) } return findCelebrity2(m) } func findCelebrity1(m [][]int) int { for i := 0; i < len(m); i++ { if !knowAny(m, i) && knownByAll(m, i) { return i } } return -1 } func findCelebrity2(m [][]int) int { c := findCandidate(m) if knownByAll(m, c) && !knowAny(m, c) { return c } return -1 }
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