minimax AI code stuck in a loop

Disclaimer: First time trying to implement a AI using minimax approach (its a turn-based game). There are not many good resources available online to learn AI (specifically minimax in C#) so I am pretty sure I messed up somewhere as I was rewriting a example I found online.

using System.Collections; using System.Collections.Generic; using UnityEngine; public class GameController : MonoBehaviour { public const int tilesX = 14; public const int tilesY = 9; public int[,] board; public GameObject redObject; public GameObject blueObject; public int currentPlayer = 1; //For AI public const int maxDepth = 7; public const int orangeWins = 1000000; public const int yellowWins = -orangeWins; public Board aiBoard; public int scoreOrig; // Use this for initialization void Start () { board = new int[tilesY, tilesX]; aiBoard = new Board(); //AI scoreOrig = ScoreBoard(aiBoard); //AI } // Update is called once per frame void Update() { if (getWinner() != 0) { return; //Game Over } if (Input.GetButtonDown("Fire1")) { //Translate mousePosition from screenSize to actual gameViewUnits Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition); //Run below function only if mouseClick's X/Y are within tileGrid mousePressed(ray); } } void mousePressed(Ray ray) { Vector2 mouseClickVector = new Vector2(ray.origin.x,ray.origin.y); int mouseClickX = (int) mouseClickVector.x; //Debug.Log(mouseClickX); int y = findNextSpace(mouseClickX); //Debug.Log("Y: "+y); if (y>=0) { board[y,mouseClickX] = currentPlayer; dropDisk(aiBoard, mouseClickX, Mycell.Orange); //AI //Spawn and animate the circleObject spawnPlayerObject(mouseClickX, y); //End and change turn changeTurn(); } } int findNextSpace(int x) { for(int y=0; y<= tilesY - 1; y++) { if(board[y,x]==0) { return y; } } return -1; } void spawnPlayerObject(int x, int y) { float posX = (float) x + 0.5f; //center in x tile float posY = (float)y + 0.5f; //center in y tile GameObject g; if(currentPlayer==1) { g = Instantiate(redObject, new Vector3(posX, posY, 0), Quaternion.identity); } else { g = Instantiate(blueObject, new Vector3(posX, posY, 0), Quaternion.identity); } } void changeTurn() { currentPlayer = currentPlayer == 1 ? 2 : 1; //check winner getWinner(); int move, score; abMinimax(true, Mycell.Orange, maxDepth, aiBoard, out move, out score); Debug.Log("Move: "+move+" | Score: "+score); Debug.Log(aiBoard); } int getWinner() //From rows,columns and diagnoals { //////////// //Columns/// /////////// for(int y=0; y<tilesY; y++) { for (int x=0; x<tilesX; x++) { if (checkTile(y,x)!=0 && checkTile(y, x) ==checkTile(y, x+1) && checkTile(y, x) == checkTile(y, x+2) && checkTile(y, x) == checkTile(y, x+3)) { Debug.Log("Won Columns: "+ checkTile(y, x)); return checkTile(y, x); } } } //////// //Rows// //////// for (int y = 0; y < tilesY; y++) { for (int x = 0; x < tilesX; x++) { if (checkTile(y, x) != 0 && checkTile(y, x) == checkTile(y+1, x) && checkTile(y, x) == checkTile(y+2, x) && checkTile(y, x) == checkTile(y+3, x)) { Debug.Log("Won Rows: " + checkTile(y, x)); return checkTile(y, x); } } } ///////////// //Diagnoals// ///////////// for (int y = 0; y < tilesY; y++) { for (int x = 0; x < tilesX; x++) { for (int d = -1; d <= 1; d += 2) { if (checkTile(y, x) != 0 && checkTile(y, x) == checkTile(y + 1 * d, x+1) && checkTile(y, x) == checkTile(y + 2 *d, x+2) && checkTile(y, x) == checkTile(y + 3 *d, x+3)) { Debug.Log("Won Diagnoals: " + checkTile(y, x)); return checkTile(y, x); } } } } /////////////////////////// //Still possible turns///// ////////////////////////// for (int y = 0; y < tilesY; y++) { for (int x = 0; x < tilesX; x++) { if (checkTile(y, x) == 0) { //Debug.Log("Still Possible turns left"); return 0; } } } //draw is default return -1; } int checkTile(int y, int x) { return (y < 0 || x < 0 || y >= tilesY || x >= tilesX) ? 0 : board[y, x]; } //////////////// //////AI/////// /////////////// public static bool g_debug = true; public enum Mycell { Orange = 1, Yellow = -1, Barren = 0 }; public class Board { // Initially, this was Mycell[,] // Unfortunately, C# 2D arrays are a lot slower // than simple arrays of arrays (Jagged arrays): Mycell[][] // BUT // using a 1D array is EVEN faster: // _slots[width*Y + X] // is much faster than // _slots[Y][X] // // (sigh) Oh well, C# is a VM-based language (specifically, .NET). // Running fast is not the primary concern in VMs... public Mycell[] _slots; public Board() { _slots = new Mycell[tilesY * tilesX]; //height * width } }; public static int dropDisk(Board board, int column, Mycell color) { for (int y = tilesY - 1; y >= 0; y--) if (board._slots[tilesX * (y) + column] == Mycell.Barren) { board._slots[tilesX * (y) + column] = color; return y; } return -1; } public static int ScoreBoard(Board board) { int[] counters = { 0, 0, 0, 0, 0, 0, 0, 0, 0 }; // Horizontal spans for (int y = 0; y < tilesY; y++) { int score = (int)board._slots[tilesX * (y) + 0] + (int)board._slots[tilesX * (y) + 1] + (int)board._slots[tilesX * (y) + 2]; for (int x = 3; x < tilesX; x++) { score += (int)board._slots[tilesX * (y) + x]; counters[score + 4]++; score -= (int)board._slots[tilesX * (y) + x - 3]; } } // Vertical spans for (int x = 0; x < tilesX; x++) { int score = (int)board._slots[tilesX * (0) + x] + (int)board._slots[tilesX * (1) + x] + (int)board._slots[tilesX * (2) + x]; for (int y = 3; y < tilesY; y++) { score += (int)board._slots[tilesX * (y) + x]; counters[score + 4]++; score -= (int)board._slots[tilesX * (y - 3) + x]; } } // Down-right (and up-left) diagonals for (int y = 0; y < tilesY - 3; y++) { for (int x = 0; x < tilesX - 3; x++) { int score = 0; for (int ofs = 0; ofs < 4; ofs++) { int yy = y + ofs; int xx = x + ofs; score += (int)board._slots[tilesX * (yy) + xx]; } counters[score + 4]++; } } // up-right (and down-left) diagonals for (int y = 3; y < tilesY; y++) { for (int x = 0; x < tilesX - 3; x++) { int score = 0; for (int ofs = 0; ofs < 4; ofs++) { int yy = y - ofs; int xx = x + ofs; score += (int)board._slots[tilesX * (yy) + xx]; } counters[score + 4]++; } } if (counters[0] != 0) return yellowWins; else if (counters[8] != 0) return orangeWins; else return counters[5] + 2 * counters[6] + 5 * counters[7] - counters[3] - 2 * counters[2] - 5 * counters[1]; } //End Scoreboard public static void abMinimax(bool maximizeOrMinimize, Mycell color, int depth, Board board, out int move, out int score) { if (0 == depth) { move = -1; score = ScoreBoard(board); } else { int bestScore = maximizeOrMinimize ? -10000000 : 10000000; int bestMove = -1; for (int column = 0; column < tilesX; column++) { if (board._slots[tilesX * (0) + column] != Mycell.Barren) continue; int rowFilled = dropDisk(board, column, color); if (rowFilled == -1) continue; int s = ScoreBoard(board); if (s == (maximizeOrMinimize ? orangeWins : yellowWins)) { bestMove = column; bestScore = s; board._slots[tilesX * (rowFilled) + column] = Mycell.Barren; break; } int moveInner, scoreInner; if (depth > 1) abMinimax(!maximizeOrMinimize, color == Mycell.Orange ? Mycell.Yellow : Mycell.Orange, depth - 1, board, out moveInner, out scoreInner); else { moveInner = -1; scoreInner = s; } board._slots[tilesX * (rowFilled) + column] = Mycell.Barren; /* when loss is certain, avoid forfeiting the match, by shifting scores by depth... */ if (scoreInner == orangeWins || scoreInner == yellowWins) scoreInner -= depth * (int)color; if (depth == maxDepth && g_debug) Debug.Log("Depth: " + depth+", placing on: " + column+", score: " + scoreInner); if (maximizeOrMinimize) { if (scoreInner >= bestScore) { bestScore = scoreInner; bestMove = column; } } else { if (scoreInner <= bestScore) { bestScore = scoreInner; bestMove = column; } } } move = bestMove; score = bestScore; } } //End abMiniMax } 

Pretty sure its stuck in abMinimax function.
And yes, its a Connect 4 (Four in a Row).