Initial commit

2020/day01/day01.c

@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    printf("Usage: %s <input file>\n", argv[0]);
+    return 0;
+  }
+
+  FILE *fp = fopen(argv[1], "r");
+  if (fp == NULL) {
+    printf("Could not open file %s\n", argv[1]);
+    return 1;
+  }
+
+  int input[1024] = {0};
+  int d;
+  int n = 0;
+  while (fscanf(fp, "%d\n", &d) == 1) {
+    input[n] = d;
+    n++;
+  }
+  fclose(fp);
+
+  int res = -1;
+  for (int i = 0; i < n && res == -1; ++i) {
+    for (int j = 0; j < n && res == -1; ++j) {
+      if (input[i] + input[j] == 2020) {
+        res = input[i] * input[j];
+        break;
+      }
+    }
+  }
+  printf("%d\n", res);
+
+  res = -1;
+  for (int i = 0; i < n && res == -1; ++i) {
+    for (int j = 0; j < n && res == -1; ++j) {
+      for (int k = 0; k < n && res == -1; ++k) {
+        if (input[i] + input[j] + input[k] == 2020) {
+          res = input[i] * input[j] * input[k];
+        }
+      }
+    }
+  }
+  printf("%d\n", res);
+
+  return 0;
+}