part one day 15

diff --git a/15a.c b/15a.c
new file mode 100644 (file)
index 0000000..3145541
--- /dev/null
+++ b/15a.c
@@ -0,0 +1,56 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <limits.h>
+#include <string.h>
+
+#define min(a, b) ((a) < (b) ? (a) : (b))
+
+int grid[100][100] = {0};
+int maxx = 0;
+int maxy = 0;
+
+int cache[100][100];
+int minimal_risk(int x, int y)
+{
+       //check bounds
+       if (x < 0 || y < 0 || x >= maxx || y >= maxy)
+               return -1;
+       //check cache
+       if (cache[y][x] != -1)
+               return cache[y][x];
+       //Calculate
+       int d = minimal_risk(x, y+1);
+       int r = minimal_risk(x+1, y);
+       if (d == -1 && r == -1) {
+               printf("shouldn't happen\n");
+               return -1;
+       } else if (d == -1) {
+               cache[y][x] = r + grid[y][x];
+       } else if (r == -1) {
+               cache[y][x] = d + grid[y][x];
+       } else {
+               cache[y][x] = min(d, r) + grid[y][x];
+       }
+       return cache[y][x];
+}
+
+int main()
+{
+       int c, x = 0;;
+       while ( (c = getchar()) != EOF) {
+               if (c == '\n') {
+                       maxx = x;
+                       x = 0;
+                       maxy++;
+               } else {
+                       grid[maxy][x++] = c-'0';
+               }
+       }
+       grid[0][0] = 0;
+       for (int y = 0; y<maxy; y++)
+               for (int x = 0; x<maxx; x++)
+                       cache[y][x] = -1;
+       cache[maxy-1][maxx-1] = grid[maxy-1][maxx-1];
+
+       printf("%d\n", minimal_risk(0, 0));
+}