Index: aoc2015.c
==================================================================
--- aoc2015.c
+++ aoc2015.c
@@ -1,10 +1,55 @@
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include "aocdailies.h"
 #include "aocutils.h"
 
+struct House {
+    int row, col;
+};
+
+#ifndef MAX_HOUSES
+#  define MAX_HOUSES 2400
+#else
+#  error MAX_HOUSES already defined
+#endif
+void aoc201503(char *data, size_t len) {
+    (void)len; // unused argument
+    struct House house[MAX_HOUSES] = {0};
+    unsigned nhouse = 1; // house at [0, 0] visited
+    int x = 0, y = 0;
+    while (*data) {
+        switch (*data) {
+            default: break;
+            case '^': y++; break;
+            case 'v': y--; break;
+            case '>': x++; break;
+            case '<': x--; break;
+        }
+        data++;
+        bool visited = false;
+        for (size_t k = 0; k < nhouse; k++) {
+            if ((house[k].row == x) && (house[k].col == y)) {
+                visited = true;
+                break;
+            }
+        }
+        if (!visited) {
+            if (nhouse == MAX_HOUSES) {
+                fprintf(stderr, "Need more houses in aoc201503()\n");
+                exit(EXIT_FAILURE);
+            }
+            house[nhouse].row = x;
+            house[nhouse].col = y;
+            nhouse += 1;
+        }
+    }
+    printf("Santa delivered at least 1 present to %u houses.\n", nhouse);
+}
+#undef MAX_HOUSES
+
 void aoc201502(char *data, size_t len) {
     (void)len; // unused argument
     unsigned sqf = 0, f = 0;
     for (;;) {
         char *err;

Index: aocdailies.c
==================================================================
--- aocdailies.c
+++ aocdailies.c
@@ -32,12 +32,12 @@
         case 201508: p = aoc201508; break;
         case 201507: p = aoc201507; break;
         case 201506: p = aoc201506; break;
         case 201505: p = aoc201505; break;
         case 201504: p = aoc201504; break;
-        case 201503: p = aoc201503; break;
         #endif
+        case 201503: p = aoc201503; break;
         case 201502: p = aoc201502; break;
         case 201501: p = aoc201501; break;
 
     }
     return p;

Index: aocdailies.h
==================================================================
--- aocdailies.h
+++ aocdailies.h
@@ -32,11 +32,11 @@
 aocfunc aoc201508;
 aocfunc aoc201507;
 aocfunc aoc201506;
 aocfunc aoc201505;
 aocfunc aoc201504;
-aocfunc aoc201503;
 #endif
+aocfunc aoc201503;
 aocfunc aoc201502;
 aocfunc aoc201501;
 
 #endif