diff --git a/day7p1/Makefile b/day7p1/Makefile
new file mode 100644
index 0000000..c711967
--- /dev/null
+++ b/day7p1/Makefile
@@ -0,0 +1,12 @@
+CFLAGS := -Wall -Wextra -std=c17 -D_GNU_SOURCE
+
+LIBS := glib-2.0
+CFLAGS += $(shell pkg-config --cflags $(LIBS))
+LDLIBS := $(shell pkg-config --libs $(LIBS))
+
+.PHONY: all
+all: main
+
+.PHONY: clean
+clean:
+	rm -f main
diff --git a/day7p1/input b/day7p1/input
new file mode 100644
index 0000000..7155300
--- /dev/null
+++ b/day7p1/input
@@ -0,0 +1,101 @@
+Step J must be finished before step H can begin.
+Step N must be finished before step C can begin.
+Step G must be finished before step P can begin.
+Step M must be finished before step I can begin.
+Step H must be finished before step X can begin.
+Step B must be finished before step Y can begin.
+Step C must be finished before step L can begin.
+Step F must be finished before step I can begin.
+Step V must be finished before step O can begin.
+Step W must be finished before step Q can begin.
+Step E must be finished before step L can begin.
+Step U must be finished before step S can begin.
+Step D must be finished before step K can begin.
+Step Y must be finished before step X can begin.
+Step T must be finished before step R can begin.
+Step I must be finished before step K can begin.
+Step A must be finished before step K can begin.
+Step L must be finished before step X can begin.
+Step Q must be finished before step S can begin.
+Step S must be finished before step O can begin.
+Step P must be finished before step Z can begin.
+Step X must be finished before step R can begin.
+Step Z must be finished before step O can begin.
+Step O must be finished before step K can begin.
+Step R must be finished before step K can begin.
+Step J must be finished before step W can begin.
+Step F must be finished before step V can begin.
+Step A must be finished before step X can begin.
+Step Z must be finished before step K can begin.
+Step M must be finished before step O can begin.
+Step X must be finished before step K can begin.
+Step E must be finished before step K can begin.
+Step J must be finished before step K can begin.
+Step E must be finished before step Y can begin.
+Step B must be finished before step Q can begin.
+Step X must be finished before step Z can begin.
+Step D must be finished before step L can begin.
+Step N must be finished before step I can begin.
+Step N must be finished before step B can begin.
+Step V must be finished before step A can begin.
+Step H must be finished before step R can begin.
+Step N must be finished before step L can begin.
+Step U must be finished before step O can begin.
+Step A must be finished before step O can begin.
+Step V must be finished before step Z can begin.
+Step O must be finished before step R can begin.
+Step Q must be finished before step P can begin.
+Step F must be finished before step Q can begin.
+Step P must be finished before step R can begin.
+Step S must be finished before step X can begin.
+Step J must be finished before step E can begin.
+Step V must be finished before step P can begin.
+Step M must be finished before step D can begin.
+Step I must be finished before step S can begin.
+Step Q must be finished before step O can begin.
+Step M must be finished before step H can begin.
+Step W must be finished before step X can begin.
+Step D must be finished before step O can begin.
+Step X must be finished before step O can begin.
+Step Y must be finished before step Z can begin.
+Step F must be finished before step L can begin.
+Step V must be finished before step T can begin.
+Step V must be finished before step E can begin.
+Step Y must be finished before step A can begin.
+Step I must be finished before step R can begin.
+Step L must be finished before step O can begin.
+Step U must be finished before step X can begin.
+Step Q must be finished before step X can begin.
+Step P must be finished before step X can begin.
+Step G must be finished before step C can begin.
+Step A must be finished before step L can begin.
+Step M must be finished before step U can begin.
+Step L must be finished before step S can begin.
+Step S must be finished before step P can begin.
+Step S must be finished before step K can begin.
+Step F must be finished before step T can begin.
+Step Q must be finished before step K can begin.
+Step G must be finished before step M can begin.
+Step G must be finished before step F can begin.
+Step T must be finished before step Q can begin.
+Step F must be finished before step Z can begin.
+Step I must be finished before step Z can begin.
+Step N must be finished before step X can begin.
+Step J must be finished before step F can begin.
+Step W must be finished before step E can begin.
+Step M must be finished before step Z can begin.
+Step G must be finished before step X can begin.
+Step V must be finished before step U can begin.
+Step P must be finished before step O can begin.
+Step U must be finished before step R can begin.
+Step G must be finished before step Z can begin.
+Step F must be finished before step R can begin.
+Step L must be finished before step R can begin.
+Step F must be finished before step A can begin.
+Step I must be finished before step O can begin.
+Step D must be finished before step T can begin.
+Step U must be finished before step L can begin.
+Step B must be finished before step S can begin.
+Step S must be finished before step Z can begin.
+Step J must be finished before step N can begin.
+Step H must be finished before step T can begin.
diff --git a/day7p1/main.c b/day7p1/main.c
new file mode 100644
index 0000000..65a6841
--- /dev/null
+++ b/day7p1/main.c
@@ -0,0 +1,107 @@
+#include <stdio.h>
+
+#include <glib.h>
+
+struct action {
+    int id;
+    GPtrArray *depends;
+    GPtrArray *required_by;
+};
+
+void free_action(gpointer data)
+{
+    struct action *action = (struct action *)data;
+    g_ptr_array_free(action->depends, TRUE);
+    g_ptr_array_free(action->required_by, TRUE);
+    g_free(action);
+}
+
+struct action *get_action(GHashTable *table, int id)
+{
+    struct action *action = g_hash_table_lookup(table, GINT_TO_POINTER(id));
+    if (action) return action;
+
+    action = g_malloc(sizeof(struct action));
+    action->depends = g_ptr_array_new();
+    action->required_by = g_ptr_array_new();
+    action->id = id;
+    g_hash_table_insert(table, GINT_TO_POINTER(id), action);
+    return action;
+}
+
+gint compare_action(gconstpointer _a, gconstpointer _b)
+{
+    struct action *a = *(struct action **)_a;
+    struct action *b = *(struct action **)_b;
+    return a->id - b->id;
+}
+
+GHashTable *parse_tree(const char *fname)
+{
+    FILE *f = fopen(fname, "r");
+    if (!f) {
+        perror(fname);
+        return NULL;
+    }
+
+    GHashTable *table = g_hash_table_new_full(NULL, NULL, NULL, free_action);
+
+    char *line = NULL;
+    size_t line_len = 0;
+    while (getline(&line, &line_len, f) != -1) {
+        char depends = 0;
+        char required_by = 0;
+        sscanf(line, "Step %c must be finished before step %c can begin.",
+                &depends, &required_by);
+
+        struct action *dependent = get_action(table, depends);
+        struct action *required = get_action(table, required_by);
+
+        g_ptr_array_add(dependent->required_by, required);
+        g_ptr_array_add(required->depends, dependent);
+    }
+
+    free(line);
+    fclose(f);
+    return table;
+}
+
+int main()
+
+{
+    GHashTable *table = parse_tree("input");
+    if (!table) return 1;
+
+    GPtrArray *queue = g_ptr_array_new();
+    GString *result = g_string_new(NULL);
+
+    // Find items without dependencies
+    GHashTableIter iter;
+    gpointer key, value;
+    g_hash_table_iter_init(&iter, table);
+    while (g_hash_table_iter_next(&iter, &key, &value)) {
+        struct action *action = (struct action *)value;
+        if (action->depends->len == 0) {
+            g_ptr_array_add(queue, action);
+        }
+    }
+
+    while (queue->len) {
+        g_ptr_array_sort(queue, compare_action);
+
+        struct action *action = g_ptr_array_remove_index_fast(queue, 0);
+        g_string_append_c(result, action->id);
+        for (unsigned i = 0; i < action->required_by->len; i++) {
+            struct action *next = g_ptr_array_index(action->required_by, i);
+            g_ptr_array_remove_fast(next->depends, action);
+            if (next->depends->len == 0) g_ptr_array_add(queue, next);
+        }
+    }
+
+    puts(result->str);
+
+    g_string_free(result, TRUE);
+    g_ptr_array_free(queue, TRUE);
+    g_hash_table_destroy(table);
+    return 0;
+}