adventofcode2022/day17/jet.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_JET_PATTERN 16*1024
#define MAX_STATINARY_ROCK_LAYERS 2*1024*1024
#define ROW_WIDTH 7
#define ROCK_TYPE_COUNT 5
#define ROCK_THRESHOLD 1000000000000ULL

typedef enum direction {
    LEFT,
    RIGHT,
} DIRECTION;

// Each rock will consist a maximum of 5 elements
// The elements array contains relative positions to the refElement
// By convention the refElement is always the position that is
// the bottom left corner of the rock's enclosing rectangle
// (Not always part of the rock itself)
// The refElement is used for universal spawning of the rocks
typedef struct rock {
    int element_count;
    int refElement[2];
    int elements[5][2];
} ROCK;

int main() {
    char c;

    DIRECTION *jetPattern;
    jetPattern = (DIRECTION*)malloc(MAX_JET_PATTERN * sizeof(DIRECTION));
    memset(jetPattern, 0, MAX_JET_PATTERN * sizeof(DIRECTION));
    unsigned jetPattern_count = 0, currJet = 0;

    while ((c = getchar()) != EOF) {
        switch (c) {
            case '<':
                jetPattern[jetPattern_count] = LEFT;
                break;
            case '>':
                jetPattern[jetPattern_count] = RIGHT;
                break;
            default:
                jetPattern_count--;
        }
        jetPattern_count++;
    }

    // We will store the stationary rocks by row
    int **rocks = (int**)malloc(MAX_STATINARY_ROCK_LAYERS * sizeof(int*));
    for (int i = 0; i < MAX_STATINARY_ROCK_LAYERS; i++) {
        rocks[i] = (int*)malloc(ROW_WIDTH * sizeof(int));
        memset(rocks[i], 0, ROW_WIDTH * sizeof(int));
    }

    // Highest rock layer
    long highestLayer = -1;

    // Define every rock type
    ROCK rockTypes[ROCK_TYPE_COUNT] = {
        { .element_count = 4, .refElement = {0, 0}, .elements = {{0,0}, {0,1}, {0,2}, {0,3}}},
        { .element_count = 5, .refElement = {0, 0}, .elements = {{1,0}, {0,1}, {1,1}, {2,1}, {1,2}}},
        { .element_count = 5, .refElement = {0, 0}, .elements = {{0,0}, {0,1}, {0,2}, {1,2}, {2,2}}},
        { .element_count = 4, .refElement = {0, 0}, .elements = {{0,0}, {1,0}, {2,0}, {3,0}}},
        { .element_count = 4, .refElement = {0, 0}, .elements = {{0,0}, {0,1}, {1,0}, {1,1}}}
    };

    int currentRock = 0;
    unsigned long long rockBottomCount = 0ULL, cumHighestLayer = 0ULL;

    while (rockBottomCount != ROCK_THRESHOLD) {
        // Handle overflow
        if (currentRock == ROCK_TYPE_COUNT) {
            currentRock = 0;
        }
        // Spawn new rock
        rockTypes[currentRock].refElement[0] = highestLayer + 4;
        rockTypes[currentRock].refElement[1] = 2;

        // Fall
        int bottom = 0;
        do {
            if (currJet == jetPattern_count) {
                currJet = 0;
            }
            // Jet
            ROCK currentPosition = rockTypes[currentRock];
            // Move to jet direction
            int xdirection = 0;
            switch (jetPattern[currJet]) {
                case LEFT:
                    xdirection = -1;
                    break;
                case RIGHT:
                    xdirection = 1;
                    break;
            }

            rockTypes[currentRock].refElement[1] += xdirection;

            int collision = 0;
            if (rockTypes[currentRock].refElement[1] == -1) {
                collision = 1;
            }
            if (!collision) {
            for (int i = 0; i < rockTypes[currentRock].element_count; i++) {
                if (rockTypes[currentRock].refElement[1] + rockTypes[currentRock].elements[i][1] == ROW_WIDTH) {
                    collision = 1;
                    break;
                }
                
                if (rocks[rockTypes[currentRock].refElement[0]+rockTypes[currentRock].elements[i][0]][rockTypes[currentRock].refElement[1]+rockTypes[currentRock].elements[i][1]]) {
                    collision = 1;
                    break;
                }
            }
            }

            if (collision) {
                rockTypes[currentRock] = currentPosition;
            }

            collision = 0;
            // Fall
            if (rockTypes[currentRock].refElement[0] == 0) {
                collision = 1;
            }
            if (!collision) {
                for (int i = 0; i < rockTypes[currentRock].element_count; i++) {
                    if (rocks[rockTypes[currentRock].refElement[0]+rockTypes[currentRock].elements[i][0]-1][rockTypes[currentRock].refElement[1]+rockTypes[currentRock].elements[i][1]]) {
                        collision = 1;
                        break;
                    }
                }
            }

            if (collision) {
                bottom = 1;
            } else {
                rockTypes[currentRock].refElement[0]--;
            }
            
            currJet++;
        } while(!bottom);

        rockBottomCount++;
        // Freeze rock
        for (int i = 0; i < rockTypes[currentRock].element_count; i++) {
            rocks[rockTypes[currentRock].refElement[0] + rockTypes[currentRock].elements[i][0]][rockTypes[currentRock].refElement[1] + rockTypes[currentRock].elements[i][1]] = 1;
            if (rockTypes[currentRock].refElement[0] + rockTypes[currentRock].elements[i][0] > highestLayer) {
                highestLayer = rockTypes[currentRock].refElement[0] + rockTypes[currentRock].elements[i][0];
            }
        }

        currentRock++;

        int repeating;

        // The commented out code below calculates the repeat period (2597)
        // in rock layers. After that you can get the number of rocks in the
        // period (1705). It also outputs the offset (302) which can also be
        // converted to number of rocks (205)
        if (rockBottomCount == 205) {
            rockBottomCount += ((ROCK_THRESHOLD-205)/1705)*1705;
            cumHighestLayer += ((ROCK_THRESHOLD-205)/1705)*2597;
        }

        // We have reached our memory limit, we must find the repeating pattern
//        if (highestLayer >= (MAX_STATINARY_ROCK_LAYERS) - 10) {
//            for (long long j = 2; j <= MAX_STATINARY_ROCK_LAYERS/32; j++) {
//                for (long long i = 0; i < j; i++) {
//                    repeating = 1;
//                    for (long long k = 1; k < (MAX_STATINARY_ROCK_LAYERS-i)/j; k++) {
//                        for (long long l = 0; l < j; l++) {
//                            if (memcmp(rocks[i+l], rocks[i+k*j+l], ROW_WIDTH) != 0) {
//                                repeating = 0;
//                                break;
//                            }
//                        }
//                        if (repeating) {
//                            break;
//                        }
//                    }
//                    if (repeating) {
//                        printf("Repeat period: %lli Repeat offset: %lli\n", j, i);
//                        break;
//                    }
//                }
//                if (repeating) {
//                    break;
//                }
//            }
//        }
//        if (repeating) {
//            break;
//        }
    }

    printf("%llu\n", cumHighestLayer + (unsigned long long)highestLayer + 1ULL);

    free(jetPattern);
    for (int i = 0; i < MAX_STATINARY_ROCK_LAYERS; i++) {
        free(rocks[i]);
    }
    free(rocks);
}