1 files changed, 43 insertions, 0 deletions
diff --git a/src/solve.rs b/src/solve.rs
new file mode 100644
index 0000000..2c7e0d2
--- /dev/null
+++ b/src/solve.rs
@@ -0,0 +1,43 @@
+use crate::position::{Position, WIDTH, HEIGHT};
+
+pub fn solve(p: Position, a: i32, b: i32) -> i32 {
+    if p.is_draw() {
+        return 0;
+    }
+    for x in 0..WIDTH {
+        if p.is_valid_play(x) && p.is_winning_play(x) {
+            return (((WIDTH * HEIGHT + 1) as i32) - (p.play_count as i32)) / 2;
+        }
+    }
+
+    let mut alpha = a;
+    let mut beta = b;
+
+    let max = (((WIDTH * HEIGHT + 1) as i32) - (p.play_count as i32)) / 2;
+
+    if beta > max {
+        beta = max;
+        if alpha >= beta {
+            return beta;
+        }
+    }
+
+    for x in 0..WIDTH {
+        if !p.is_valid_play(x) {
+            continue
+        }
+
+        let score = -solve(p.play(x), -beta, -alpha);
+
+        if score >= beta {
+            return score;
+        }
+
+        if score > alpha {
+            alpha = score;
+        }
+    }
+    return alpha;
+}
+
+