day 21 part 1

2021/day21/aoc-c.c

@@ -20,10 +20,57 @@
 #include "bits.h"
 #include "list.h"
 
+typedef struct {
+    int score;
+    int pos;
+} player_t;
+
+static player_t players[2];
+
+static int nrolls = 0;
+
+static inline int do_roll()
+{
+    static int roll = 0;
+    int res = 0;
+
+    for (int i = 0; i < 3; ++i) {
+        res += roll++ % 100 + 1;
+        nrolls++;
+    }
+    return res % 10;
+}
+
+static int player_turn(int player)
+{
+    int roll;
+
+    roll = do_roll();
+    players[player].pos += roll;
+    if (!(players[player].pos % 10))
+        players[player].pos = 10;
+    else
+        players[player].pos %= 10;
+
+    players[player].score += players[player].pos;
+    log_f(1, "player %d: nrolls=%d roll=%d pos=%d score=%d\n", player+1,
+          nrolls, roll,
+          players[player].pos, players[player].score);
+    return players[player].score;
+}
+
 static int part1()
 {
+    while (1) {
+        if (player_turn(0) >= 1000)
+            return players[1].score * nrolls;
+        if (player_turn(1) >= 1000)
+            return players[0].score * nrolls;
+    }
+
     return 1;
 }
+
 static int part2()
 {
     return 1;
@@ -35,6 +82,12 @@ static int usage(char *prg)
     return 1;
 }
 
+static void read_input()
+{
+    scanf("Player %*c starting position: %d\n", &players[0].pos);
+    scanf("Player %*c starting position: %d\n", &players[1].pos);
+}
+
 int main(int ac, char **av)
 {
     int opt, part = 1;
@@ -56,6 +109,9 @@ int main(int ac, char **av)
     if (optind < ac)
         return usage(*av);
 
+    read_input();
+    printf("player1: %d\n", players[0].pos);
+    printf("player1: %d\n", players[1].pos);
     printf("%s : res=%d\n", *av, part == 1? part1(): part2());
 
     exit(0);