first commit

.gitignore

@@ -0,0 +1 @@
+/target

app.cpp

@@ -0,0 +1,229 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+#define ArrayCount(arr) (sizeof(arr) / sizeof((arr)[0]))
+
+typedef int8_t int8;
+typedef int16_t int16;
+typedef int32_t int32;
+typedef int64_t int64;
+typedef uint8_t uint8;
+typedef uint16_t uint16;
+typedef uint32_t uint32;
+typedef uint64_t uint64;
+typedef uint8 byte;
+typedef uint16 b16;
+typedef uint32 b32;
+typedef uint64 b64;
+typedef float real32;
+typedef double real64;
+
+struct string {
+    uint8 *str;
+    size_t len;
+};
+
+struct StringNode {
+    string *str;
+    size_t start;
+    size_t end;
+};
+
+string asString(StringNode *node) {
+    return {
+        node->str->str + node->start,
+        node->end - node->start,
+    };
+}
+
+string createStr(byte *str, size_t len) { 
+    string result;
+    result.str = str;
+    result.len = len;
+    return result;
+}
+
+#define strlit(lit) createStr((byte *)(lit), sizeof(lit) - 1)
+
+#define Bytes(n)      (n)
+#define Kilobytes(n)  (n << 10)
+#define Megabytes(n)  (n << 20)
+#define Gigabytes(n)  (((uint64)n) << 30)
+#define Terabytes(n)  (((uint64)n) << 40)
+
+#define Thousand(n) ((n)*1000)
+#define Million(n)  ((n)*1000000)
+#define Billion(n)  ((n)*1000000000LL)
+
+struct Arena {
+    void *memory;
+    size_t capacity;
+    size_t head;
+};
+
+void *pushSize(Arena *arena, size_t size) {
+    if (arena->capacity - arena->head >= size) {
+        arena->head += size;
+        return (char *)arena->memory + arena->head + size;
+    }
+    return 0;
+}
+
+#define PushArray(arena, type, size) (type *)pushSize(arena, sizeof(type) * (size))
+#define PushStruct(arena, type, size) (type *)pushSize(arena, sizeof(type))
+
+Arena createArena(size_t capacity) {
+    Arena result = {};
+    result.memory = mmap(0, capacity, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+    result.capacity = capacity;
+    result.head = 0;
+    return result;
+}
+
+size_t getFileSize(string file) {
+    struct stat st;
+    stat((char *)file.str, &st);
+    return st.st_size;
+}
+
+struct Buffer {
+    size_t size;
+    byte *data;
+};
+
+Buffer readEntireFile(Arena *arena, string file) {
+    FILE *input = fopen((char *)file.str, "r");
+    size_t filesize = getFileSize(file);
+    byte *readBuffer = PushArray(arena, byte, filesize);
+    fread(readBuffer, sizeof(byte), filesize, input);
+    fclose(input);
+    return { filesize, readBuffer };
+}
+
+int cmpint(const void *a, const void *b) {
+    int *x = (int *)a;
+    int *y = (int *)b;
+    return (*x > *y) - (*x < *y);
+}
+
+int day1() {
+    Arena arena = createArena(Megabytes(16));
+
+    Buffer file = readEntireFile(&arena, strlit("./day-1-input"));
+
+    int LIST_SIZE = 1000;
+    int *firsts = PushArray(&arena, int, LIST_SIZE);
+    int *seconds = PushArray(&arena, int, LIST_SIZE);
+
+    char currentNum[5];
+    int numIndex = 0;
+    int line = 0;
+    int *target = firsts;
+
+    for (int i = 0; i < file.size; i++) {
+        char c = file.data[i];
+        if (c == ' ') {
+            continue;
+        } else if (c == '\n') {
+            line++;
+            continue;
+        } else {
+            currentNum[numIndex++] = c;
+        }
+        if (numIndex == 5) {
+            target[line] = atoi(currentNum);
+            if (target == firsts) {
+                target = seconds;
+            } else {
+                target = firsts;
+            }
+            numIndex = 0;
+        }
+    }
+
+    qsort(firsts, line, sizeof(int), cmpint);
+    qsort(seconds, line, sizeof(int), cmpint);
+
+    int sum = 0;
+    for (int i = 0; i < line; i++) {
+        int dist = firsts[i] - seconds[i];
+        if (dist < 0) {
+            dist *= -1;
+        }
+        sum += dist;
+    }
+    printf("%i\n", sum);
+
+    // Part 2
+
+    int total = 0;
+    for (int i = 0; i < line; i++) {
+        int firstElement = firsts[i];
+        int countInSecondList = 0;
+        for (int j = 0; j < line; j++) {
+            if (seconds[j] == firstElement) {
+                countInSecondList++;
+            }
+        }
+        total += firstElement * countInSecondList;
+    }
+    printf("%i\n", total);
+
+    return 0;
+}
+
+int day2_main() {
+    Arena arena = createArena(Megabytes(16));
+    Buffer file = readEntireFile(&arena, strlit("./day-2-input"));
+
+    int safes = 0;
+    int lines  = 0;
+    int *nums = PushArray(&arena, int, 100);
+    int numLen = 1;
+    int index = 0;
+    while (index < file.size) {
+        int linestart = index;
+        int lineend = index;
+        while (file.data[lineend] != '\n' && lineend < file.size) {
+            lineend++;
+        }
+        lines++;
+        char numStr[16] = {};
+        int numStrLen = 1;
+        numLen = 1;
+        for (int j = linestart; j < lineend; j++) {
+            if (file.data[j] != ' ') {
+                numStr[numStrLen++ - 1] = file.data[j];
+            } else {
+                numStr[numStrLen - 1] = '\0';
+                nums[numLen++ - 1] = atoi(numStr);
+                numStrLen = 1;
+            }
+        }
+        bool increasing = nums[0] < nums[1];
+        bool safe = true;
+        for (int j = 0; j < numLen; j++) {
+            int diff = increasing ? nums[j + 1] - nums[j] : nums[j] - nums[j + 1];
+            if (increasing && (diff < 1 || diff > 3)) {
+                safe = false;
+                break;
+            }
+        }
+        if (safe) {
+            safes++;
+        }
+        index = lineend + 1;
+    }
+
+    printf("safes: %i", safes);
+    printf("lines: %i", lines);
+
+    return 0;
+}
+
+int main() {
+    return day2_main();
+}

build

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+#!/bin/bash
+
+clang ./app.cpp -o ./target/app

run

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+#!/bin/bash
+
+./target/app "$@"