Day 1 Check In

.gitignore

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+.idea
+cmake-build-*

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.20)
+project(aoc_2021 C)
+
+set(CMAKE_C_STANDARD 99)
+
+add_executable(aoc_2021 src/main.c src/day_1.c src/day.h)

README.md

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+# Advent of C(ode) 2021
+[AOC 2021](https://adventofcode.com/2021) attempt using C. Trying to keep it bare bones, minimal dependencies, no malloc,
+the pain of c, etc.

src/day.h

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+#ifndef AOC_2021_DAY_H
+#define AOC_2021_DAY_H
+
+int day_1();
+
+#endif //AOC_2021_DAY_H

src/day_1.c

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+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <limits.h>
+
+#include "day.h"
+
+#define DATA_MAX_LEN 2048
+
+int parse_long_from_buff(char * buffer, int64_t * val) {
+    *val = strtol(buffer, NULL, 16);
+
+    if (*val == LONG_MIN || *val == LONG_MAX) {
+        return -2;
+    }
+
+    return 0;
+}
+
+int read_input(const char * file_path, int64_t *data, uint16_t max_len) {
+    char buffer[64];
+    int c;
+    int ret = 0;
+    FILE * file = fopen(file_path, "r");
+    int data_ndx = 0;
+
+    if (file != NULL) {
+        int buffer_ndx = 0;
+        while ((c = fgetc(file)) != EOF) {
+            if (c == '\n') {
+                buffer[buffer_ndx] = 0;
+
+                ret = parse_long_from_buff(buffer, &data[data_ndx]);
+
+                if (ret < 0) {
+                    break;
+                }
+
+                data_ndx++;
+
+                if (data_ndx >= max_len) {
+                    ret = -3;
+                    break;
+                }
+
+                buffer_ndx = 0;
+            }
+            else {
+                buffer[buffer_ndx] = (char)c;
+                buffer_ndx++;
+            }
+        }
+
+        if (buffer_ndx > 0) {
+            ret = parse_long_from_buff(buffer, &data[data_ndx]);
+
+            if (ret == 0) {
+                data_ndx++;
+            }
+        }
+    }
+    else {
+        ret = -1;
+    }
+
+    if (ret == 0) {
+        ret = data_ndx;
+    }
+
+    if (file != NULL) {
+        fclose(file);
+    }
+
+    return ret;
+}
+
+void part_1(const int64_t * data, uint16_t data_len) {
+    int64_t last_value;
+    int16_t inc_count = 0;
+
+    last_value = data[0];
+    for (uint16_t i = 1; i < (uint16_t)data_len; i++) {
+        if (data[i] > last_value) {
+            inc_count++;
+        }
+
+        last_value = data[i];
+    }
+    printf("PART 1: %d values increased!\n", inc_count);
+}
+
+void part_2(const int64_t * data, uint16_t data_len) {
+    int64_t old_window_sum;
+    int64_t window_sum;
+    int16_t inc_count = 0;
+
+    old_window_sum = data[0] + data[1] + data[2];
+
+    for (uint16_t i = 3; i < (uint16_t)data_len; i++) {
+        window_sum = old_window_sum - data[i-3] + data[i];
+
+        if (window_sum > old_window_sum) {
+            inc_count++;
+        }
+
+        old_window_sum = window_sum;
+
+    }
+    printf("PART 2: %d windows increased!\n", inc_count);
+}
+
+int day_1() {
+    char * path = "../inputs/day_1.txt";
+    int data_len;
+    int64_t data[DATA_MAX_LEN];
+
+    data_len = read_input(path, data, DATA_MAX_LEN);
+
+    if (data_len < 0) {
+        printf("read_input returned an error: %d\n", data_len);
+        return data_len;
+    }
+
+    part_1(data, data_len);
+
+    part_2(data, data_len);
+
+    return 0;
+}

src/main.c

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+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "day.h"
+
+int main(int argc, char * argv[]) {
+    uint64_t day_number;
+
+    if (argc < 2) {
+        printf("Advent of **C**ode\n");
+        printf("%s DAY_NUMBER", argv[0]);
+        return -1;
+    }
+
+    day_number = strtol(argv[1], NULL, 10);
+
+    switch (day_number) {
+        case 1:
+            day_1();
+            break;
+        default:
+            printf("Invalid day ding dong!\n");
+            return -2;
+    }
+}