From b3636d404715899724753ce727e9d6df87da7a17 Mon Sep 17 00:00:00 2001
From: eug-vs <eugene@eug-vs.xyz>
Date: Thu, 18 Aug 2022 04:53:47 +0300
Subject: feat: count up to 3 moves ahead

---
 src/main.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

(limited to 'src')

diff --git a/src/main.c b/src/main.c
index 338952f..644e869 100644
--- a/src/main.c
+++ b/src/main.c
@@ -187,7 +187,7 @@ int apply_move(int move[2], int* board) {
   return board[destination];
 }
 
-int estimate_board(int* board, int color) {
+int compute_advantage(int* board, int color) {
   int counter = 0;
   for (int rank = 7; rank >= 0; rank--) {
     for (int file = 0; file < 8; file++) {
@@ -217,10 +217,9 @@ int estimate_board(int* board, int color) {
   return counter;
 }
 
-void find_best_move(int* board, int color) {
+void find_best_move(int best_move[2], int* board, int color, int depth) {
   int fake_board[128];
-  int best_estimate = -10000;
-  int best_move[2];
+  int best_advantage = -10000;
 
 
   for (int rank = 7; rank >= 0; rank--) {
@@ -241,9 +240,17 @@ void find_best_move(int* board, int color) {
               }
 
               apply_move(move, fake_board);
-              int estimate = estimate_board(fake_board, color);
-              if (estimate > best_estimate) {
-                best_estimate = estimate;
+
+              // Try finding a response
+              if (depth) {
+                int response_move[2];
+                find_best_move(response_move, fake_board, color ^ 1, depth - 1);
+                apply_move(response_move, fake_board);
+              }
+
+              int advantage = compute_advantage(fake_board, color);
+              if (advantage > best_advantage) {
+                best_advantage = advantage;
                 best_move[0] = move[0];
                 best_move[1] = move[1];
               }
@@ -257,7 +264,7 @@ void find_best_move(int* board, int color) {
   char move_in_notation[] = "xy XY";
   index_to_notation(best_move[0], move_in_notation);
   index_to_notation(best_move[1], move_in_notation + 3);
-  printf("Best move for %i is %s with score %i\n", color, move_in_notation, best_estimate);
+  if (depth == 3) printf("Best move for %i is %s with score %i\n", color, move_in_notation, best_advantage);
 }
 
 int main() {
@@ -270,9 +277,9 @@ int main() {
   int color = 0;
 
   while (1) {
-    printf("Current board estimate is %i\n", estimate_board(board, color));
+    printf("Current board advantage is %i\n", compute_advantage(board, color));
+    find_best_move(move, board, color, 3);
     printf("Enter a move for %s:\n", COLORS[color]);
-    find_best_move(board, color);
     input_move(move);
 
     int error = validate_move(move, color, board);
-- 
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