Sync

Task/Monty-Hall-problem/Go/monty-hall-problem.go

@@ -1,63 +1,27 @@
 package main
 
 import (
-    "fmt"
-    "math/rand"
+	"fmt"
+	"math/rand"
+	"time"
 )
 
 func main() {
-    games := 1000000
-    var switchWinsCar, keepWinsCar int
-    for i := 0; i < games; i++ {
-        // simulate game
-        carDoor := rand.Intn(3)
-        firstChoice := rand.Intn(3)
-        var hostOpens int
-        if carDoor == firstChoice {
-            hostOpens = rand.Intn(2)
-            if hostOpens >= carDoor {
-                hostOpens++
-            }
-        } else {
-            hostOpens = 3 - carDoor - firstChoice
-        }
-        remainingDoor := 3 - hostOpens - firstChoice
+	games := 100000
+	r := rand.New(rand.NewSource(time.Now().UnixNano()))
 
-        // some assertions that above code produced a valid game state
-        if carDoor < 0 || carDoor > 2 {
-            panic("car behind invalid door")
-        }
-        if firstChoice < 0 || firstChoice > 2 {
-            panic("contestant chose invalid door")
-        }
-        if hostOpens < 0 || hostOpens > 2 {
-            panic("host opened invalid door")
-        }
-        if hostOpens == carDoor {
-            panic("host opened door with car")
-        }
-        if hostOpens == firstChoice {
-            panic("host opened contestant's first choice")
-        }
-        if remainingDoor < 0 || remainingDoor > 2 {
-            panic("remaining door invalid")
-        }
-        if remainingDoor == firstChoice {
-            panic("remaining door same as contestant's first choice")
-        }
-        if remainingDoor == hostOpens {
-            panic("remaining door same as one host opened")
-        }
-
-        // tally results
-        if firstChoice == carDoor {
-            keepWinsCar++
-        }
-        if remainingDoor == carDoor {
-            switchWinsCar++
-        }
-    }
-    fmt.Println("In", games, "games,")
-    fmt.Println("switching doors won the car", switchWinsCar, "times,")
-    fmt.Println("keeping same door won the car", keepWinsCar, "times.")
+	var switcherWins, keeperWins, shown int
+	for i := 0; i < games; i++ {
+		doors := []int{0, 0, 0}
+		doors[r.Intn(3)] = 1 // Set which one has the car
+		choice := r.Intn(3) // Choose a door
+		for shown = r.Intn(3); shown == choice || doors[shown] == 1; shown = r.Intn(3) {}
+		switcherWins += doors[3 - choice - shown]
+		keeperWins += doors[choice]
+	}
+	floatGames := float32(games)
+	fmt.Printf("Switcher Wins: %d (%3.2f%%)\n",
+		switcherWins, (float32(switcherWins) / floatGames * 100))
+	fmt.Printf("Keeper Wins: %d (%3.2f%%)",
+		keeperWins, (float32(keeperWins) / floatGames * 100))
 }