From 2b81df57cf6482ce1e2c718d5180e3fbe2f0df50 Mon Sep 17 00:00:00 2001
From: Eric Chou <yphbchou0911@gmail.com>
Date: Thu, 13 Mar 2025 00:50:54 +0800
Subject: [PATCH] Reject row number 0 as invalid input

This update adds validation to reject row number 0, which was
previously allowed. While row numbers exceeding BOARD_SIZE were
already handled, there was no explicit check for 0. An error is now
triggered when 0 is entered.

Co-authored-by: charliechiou <charlie910417@gmail.com>
---
 main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/main.c b/main.c
index 7508167..f269c62 100644
--- a/main.c
+++ b/main.c
@@ -85,6 +85,12 @@ static int get_input(char player)
             parseX = 0;
             if (isdigit(line[i])) {
                 y = y * 10 + line[i] - '0';
+                // index cannot be 0
+                if (y == 0) {
+                    printf("Invalid operation: index cannot be 0\n");
+                    x = y = 0;
+                    break;
+                }
                 if (y > BOARD_SIZE) {
                     // could be any value in [BOARD_SIZE + 1, INT_MAX]
                     y = BOARD_SIZE + 1;