1 files changed, 21 insertions, 0 deletions

diff --git a/2021/day04.c b/2021/day04.c
index 88bf80f..c414f81 100644
--- a/2021/day04.c
+++ b/2021/day04.c
@@ -50,4 +50,25 @@ int main(void) {
 		if (!(boards[w].mark & (1 << i))) sum += boards[w].nums[i];
 	}
 	printf("%d\n", sum * num);
+	for (; i < n; ++i) {
+		for (int j = 0; j < len; ++j) {
+			for (int k = 0; k < 25; ++k) {
+				if (boards[j].nums[k] == nums[i]) {
+					int won = win(&boards[j]);
+					boards[j].mark |= 1 << k;
+					if (!won && win(&boards[j])) {
+						w = j;
+						num = nums[i];
+						sum = 0;
+						for (int i = 0; i < 25; ++i) {
+							if (!(boards[w].mark & (1 << i))) {
+								sum += boards[w].nums[i];
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+	printf("%d\n", sum * num);
 }