add day 1

.vscode/launch.json

@@ -6,7 +6,7 @@
             "request": "launch",
             "name": "Launch",
             "program": "${workspaceFolder}/build/adventofcode/adventofcode",
-            "args": ["2024", "1", "1"],
+            "args": ["2024", "1", "2"],
             "cwd": "${workspaceFolder}",
             "preLaunchTask": "CMake: build",
         }

2024/CMakeLists.txt

@@ -13,6 +13,7 @@ endforeach()
 add_custom_target(prebuild_target DEPENDS ${adv_input})
 
 add_dependencies(2024 prebuild_target)
+target_link_libraries(2024 m)
 target_sources(2024
     PRIVATE 
     src/day1.c

2024/src/day1.c

@@ -1,3 +1,116 @@
-void *day_1_part_1() {
-    return "yes";
+#include "include/days.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <inttypes.h>
+
+struct list_ctx {
+    u_int32_t* list;
+    size_t list_len;
+};
+struct list_pair {
+    struct list_ctx *left;
+    struct list_ctx *right;
+};
+
+struct list_pair *parse_input() {
+    struct list_pair *ctx = malloc(sizeof(struct list_pair));
+    ctx->left = malloc(sizeof(struct list_ctx));
+    ctx->left->list = malloc(1000 * sizeof(u_int32_t));
+    ctx->left->list_len = 1000;
+    ctx->right = malloc(sizeof(struct list_ctx));
+    ctx->right->list = malloc(1000 * sizeof(u_int32_t));
+    ctx->right->list_len = 1000;
+
+    int list_i = 0;
+    int list_buf_len = 0;
+    char *list_buf = NULL; 
+    for(int i = 0; i < input_day1_txt_len; i++) {
+        char c = input_day1_txt[i];
+        switch(c) {
+            case ' ': 
+                if (list_buf_len) {
+                    ctx->left->list[list_i] = strtoul(list_buf, NULL, 10);
+                    list_buf_len = 0;
+                    list_buf = NULL;
+                };
+                break;
+            case '\n': { 
+                ctx->right->list[list_i] = strtoul(list_buf, NULL, 10);
+                list_i++;
+                list_buf_len = 0;
+                list_buf = NULL;
+                break;
+            }
+            default: {
+                list_buf_len++;
+                list_buf = realloc(list_buf, list_buf_len * sizeof(char));
+                list_buf[list_buf_len-1] = c;
+            }
+        }
+    }
+    return ctx;
+}
+
+void selection_sort(struct list_ctx *ctx) {
+    for(int start_i = 0; start_i < ctx->list_len; start_i++) {
+        size_t min_i = start_i;
+        for (size_t i = start_i + 1; i < ctx->list_len; i++) {
+            if (ctx->list[i] < ctx->list[min_i]) {
+                min_i = i;
+            }
+        }
+        if (min_i != start_i) {
+            u_int32_t t = ctx->list[start_i];
+            ctx->list[start_i] = ctx->list[min_i];
+            ctx->list[min_i] = t;
+        }
+    }
+} 
+
+char *day_1_part_1() {
+    struct list_pair *pair = parse_input();
+
+    selection_sort(pair->left);
+    selection_sort(pair->right);
+
+    int total = 0;
+    for(int i = 0; i < 1000; i++) 
+        total += pair->left->list[i] > pair->right->list[i] ? pair->left->list[i] - pair->right->list[i] : pair->right->list[i] - pair->left->list[i];
+
+    free(pair->left->list);
+    free(pair->right->list);
+    free(pair->left);
+    free(pair->right);
+    free(pair);
+
+    int len = snprintf(NULL, 0, "%d", total);
+    char *total_str = malloc(len +1);
+    snprintf(total_str, len, "%d", total); 
+        
+    return total_str;
+}
+
+char *day_1_part_2() {
+    struct list_pair *pair = parse_input();
+    int total = 0;
+
+    // TODO: do not the O(n^2)
+    for(int left_i = 0; left_i < pair->left->list_len; left_i++) {
+        int c = 0;
+        for(int right_i = 0; right_i < pair->right->list_len; right_i++) 
+            if(pair->left->list[left_i] == pair->right->list[right_i]) c++;
+        total += c*pair->left->list[left_i];
+    }
+
+    free(pair->left->list);
+    free(pair->right->list);
+    free(pair->left);
+    free(pair->right);
+    free(pair);
+
+    int len = snprintf(NULL, 0, "%d", total) + 1;
+    char *total_str = malloc(len);
+    snprintf(total_str, len, "%d", total); 
+        
+    return total_str;
 }

2024/src/include/days.h

@@ -1,3 +1,3 @@
-#include "day1.h"
+#include "day1_input.h"
 
 char *day_1_part_1(void);

adventofcode/src/main.c

@@ -43,9 +43,11 @@ int main(int argc, char** argv) {
                 char *(*part_func)(void) = dlsym(handle, fname);
 
                 if(part_func) {
-                    fprintf(stderr, "day %s part %s: %s\n", argv[2], argv[3], part_func());
+                    char *r = part_func();
+                    fprintf(stderr, "day %s part %s: %s\n", argv[2], argv[3], r);
+                    free(r);
                 } else {
-                    fprintf(stderr, "Failed to call %s", fname);
+                    fprintf(stderr, "Failed to call %s: implementation missing!\n", fname);
                     err = 4;
                 }