advent-of-code-2024/app.cpp

#include <math.h>
#include "core.hpp"

int day1() {
    Arena arena = createArena(Megabytes(16));

    list<char> 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.length; 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));
    list<char> file = readEntireFile(&arena, strlit("./day-2-input"));

    int safes = 0;
    int lines = 0;
    int fileReadIndex = 0;
    list<int> nums = PushList(&arena, int, 100);
    list<char> numStr = PushList(&arena, char, 16);
    list<int> modifiedNums = PushList(&arena, int, nums.capacity);
    while (fileReadIndex < file.length) {
        int linestart = fileReadIndex;
        int lineend = fileReadIndex;
        while (file.data[lineend] != '\n' && lineend < file.length) {
            lineend++;
        }
        lines++;

        zeroList(&nums);
        for (int j = linestart; j < lineend; j++) {
            if (file.data[j] != ' ') {
                appendList(&numStr, (char)file.data[j]);
            } 
            if (file.data[j] == ' ' || j == lineend - 1) {
                appendList(&numStr, '\0');
                appendList(&nums, atoi(numStr.data));
                zeroList(&numStr);
            }
        }

        int unsafes = 0;
        for (int i = 0; i < nums.length + 1; i++) {
            int skipIndex = i - 1;
            zeroList(&modifiedNums);
            for (int modifiedIndex = 0; modifiedIndex < nums.length; modifiedIndex++) {
                if (modifiedIndex == skipIndex) {
                    continue;
                }
                appendList(&modifiedNums, nums.data[modifiedIndex]);
            }

            bool increasing = modifiedNums.data[0] < modifiedNums.data[1];
            bool safe = true;
            for (int checkIndex = 0; checkIndex < modifiedNums.length - 1; checkIndex++) {
                int next = checkIndex + 1;
                int diff = increasing ? modifiedNums.data[next] - modifiedNums.data[checkIndex] : modifiedNums.data[checkIndex] - modifiedNums.data[next];
                if (diff < 1 || diff > 3) {
                    safe = false;
                    break;
                }
            }
            if (!safe) {
                unsafes += 1;
            } else {
                break;
            }
        }

        if (unsafes <= nums.length) {
            safes++;
        }
        fileReadIndex = lineend + 1;
    }

    printf("safes: %i", safes);
    printf("\n");
    printf("lines: %i", lines);
    printf("\n");
    printf("Arena: %zu, %zu", arena.head, arena.capacity);
    printf("\n");

    return 0;
}

bool stringContains(string str, char c) {
    for (size_t i = 0; i < str.len; i++) {
        if (str.str[i] == c) {
            return true;
        }
    }
    return false;
}

const char NUMERIC_CHARS[] = "1234567890";
inline bool isNumeric(char c) {
    return stringContains(strlit(NUMERIC_CHARS), c);
}

inline int parsePositiveInt(string str, size_t *lengthPointer) {
    size_t numEnd = 0;
    char currChar = str.str[numEnd];
    while (numEnd < str.len && isNumeric(currChar)) {
        currChar = str.str[++numEnd];
        *lengthPointer += 1;
    }
    *lengthPointer -= 1;
    if (numEnd > 0) {
        int result = 0;
        for (int i = 0; i < numEnd; i++) {
            result *= 10;
            result += (double)(str.str[i] - '0');
        }
        return result;
    } else {
        return -1;
    }
}

int day3_main() {
    Arena arena = createArena(Megabytes(16));
    list<char> file = readEntireFile(&arena, strlit("./day-3-input"));

    string mulBegin = strlit("mul(");
    string doIdent = strlit("do()");
    string dontIdent = strlit("don't()");

    int result = 0;
    size_t c = 0;
    bool skip = false;
    while (c < file.length) {
        if (!skip) {
            if (file.data[c] == 'm') {
                string segment = strSlice(file.data, c, c+mulBegin.len);
                int first = -1;
                int second = -1;
                if (strEql(segment, mulBegin)) {
                    c += segment.len;
                    first = parsePositiveInt(strSlice(file.data, c, file.length - c), &c);
                    if (file.data[c + 1] == ',') {
                        c += 2;
                        second = parsePositiveInt(strSlice(file.data, c, file.length - c), &c);
                        if (second != -1 && file.data[c + 1] == ')') {
                            c += 1;
                            result += first * second;
                        }
                    }
                }
            } else if (file.data[c] == 'd') {
                string segment = strSlice(file.data, c, c+dontIdent.len);
                if (strEql(segment, dontIdent)) {
                    skip = true;
                    c += dontIdent.len - 1;
                }
            }
        } else {
            if (file.data[c] == 'd') {
                string segment = strSlice(file.data, c, c+doIdent.len);
                if (strEql(segment, doIdent)) {
                    skip = false;
                    c += doIdent.len - 1;
                }
            }
        } 
        c++;
    }

    printf("total: %i\n", result);

    return 0;
}

int day4_main() {
    Arena mainArena = createArena(Megabytes(16));
    Arena *arena = &mainArena;
    list<char> file = readEntireFile(arena, strlit("./day-4-input"));

    int fileReadIndex = 0;
    int lines = 0;
    int lineLength = 0;
    while (fileReadIndex < file.length) {
        int linestart = fileReadIndex;
        int lineend = fileReadIndex;
        while (file.data[lineend] != '\n' && lineend < file.length) {
            lineend++;
        }
        if (lineLength == 0) {
            lineLength = lineend - linestart;
        } else if (lineend - linestart != lineLength) {
            fputs("Bad input. One or more lines aren't the same length as the first line.", stderr);
            return 1;
        }
        lines++;
        fileReadIndex += lineLength + 1;
    }

    string xmas = strlit("XMAS");
    int count = 0;
    for (int c = 0; c < file.length; c++) {
        string strings[] = {
            //forwards 
            strSlice(file.data, c, c+xmas.len),
            //down 
            strSlice(file.data, c, c+xmas.len),
            //forwardsReverse 
            strReverse(arena, strSlice(file.data, c, c+xmas.len)),
            //downReverse 
            strReverse(arena, strSlice(file.data, c, c+xmas.len)),
        };
        for (size_t i = 0; i < ArrayCount(strings); i++) {
            if (strEql(strings[i], xmas)) {
                c += xmas.len;
                count++;
            }
        }
    }

    printf("count: %i\n", count);

    return 0;
}

int main() {
    return day4_main();
}