June 2018 Update

Task/Tic-tac-toe/Kotlin/tic-tac-toe.kotlin

@@ -0,0 +1,107 @@
+// version 1.1.51
+
+import java.util.Random
+
+val r = Random()
+val b = Array(3) { IntArray(3) }  // board -> 0: blank; -1: computer; 1: human
+
+var bestI = 0
+var bestJ = 0
+
+fun checkWinner(): Int {
+    for (i in 0..2) {
+        if (b[i][0] != 0 && b[i][1] == b[i][0] && b[i][2] == b[i][0]) return b[i][0]
+        if (b[0][i] != 0 && b[1][i] == b[0][i] && b[2][i] == b[0][i]) return b[0][i]
+    }
+    if (b[1][1] == 0) return 0
+    if (b[1][1] == b[0][0] && b[2][2] == b[0][0]) return b[0][0]
+    if (b[1][1] == b[2][0] && b[0][2] == b[1][1]) return b[1][1]
+    return 0
+}
+
+fun showBoard() {
+    val t = "X O"
+    for (i in 0..2) {
+        for (j in 0..2) print("${t[b[i][j] + 1]} ")
+        println()
+    }
+    println("-----")
+}
+
+fun testMove(value: Int, depth: Int): Int {
+    var best = -1
+    var changed = 0
+    var score = checkWinner()
+    if (score != 0) return if (score == value) 1 else -1
+    for (i in 0..2) {
+        for (j in 0..2) {
+            if (b[i][j] != 0) continue
+            b[i][j] = value
+            changed = value
+            score = -testMove(-value, depth + 1)
+            b[i][j] = 0
+            if (score <= best) continue
+            if (depth == 0) {
+                bestI = i
+                bestJ = j
+            }
+            best = score
+        }
+    }
+    return if (changed != 0) best else 0
+}
+
+fun game(user: Boolean): String {
+    var u = user
+    for (i in 0..2) b[i].fill(0)
+    print("Board postions are numbered so:\n1 2 3\n4 5 6\n7 8 9\n")
+    print("You have O, I have X.\n\n")
+
+    for (k in 0..8) {
+        while (u) {
+            var move: Int?
+            do {
+                print("Your move: ")
+                move = readLine()!!.toIntOrNull()
+            }
+            while (move != null && move !in 1..9)
+            move = move!! - 1
+            val i = move / 3
+            val j = move % 3
+            if (b[i][j] != 0) continue
+            b[i][j] = 1
+            break
+        }
+        if (!u) {
+            if (k == 0) { // randomize if computer opens, less boring
+                bestI = r.nextInt(Int.MAX_VALUE) % 3
+                bestJ = r.nextInt(Int.MAX_VALUE) % 3
+            }
+            else testMove(-1, 0)
+            b[bestI][bestJ] = -1
+            val myMove = bestI * 3 + bestJ + 1
+            println("My move: $myMove")
+        }
+        showBoard()
+        val win = checkWinner()
+        if (win != 0) return (if (win == 1) "You win" else "I win") + ".\n\n"
+        u = !u
+    }
+    return "A draw.\n\n"
+}
+
+fun main(args: Array<String>) {
+    var user = false
+    while (true) {
+        user = !user
+        print(game(user))
+        var yn: String
+        do {
+            print("Play again y/n: ")
+            yn = readLine()!!.toLowerCase()
+        }
+        while (yn != "y" && yn != "n")
+        if (yn != "y") return
+        println()
+    }
+}