291 lines
8.6 KiB
Text
291 lines
8.6 KiB
Text
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/* Require bison minimal version */
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%require "3.2"
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/* write out a header file containing the token defines */
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%header
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// Code for the header file generated by bison
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%code requires {
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typedef void* yyscan_t;
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struct parser_state {
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/// Layout of the data: forest[row][col]
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unsigned short **forest;
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size_t rows;
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size_t cols;
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unsigned short *current_line;
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/// for tracking the current position in a line during parsing
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size_t pos;
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size_t allocated;
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};
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}
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// Code for the c file
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%{
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdbool.h>
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#include "parser.h"
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#include "lexer.h"
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void yyerror(struct parser_state* state, yyscan_t scanner, const char* msg) {
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(void)state;
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(void)scanner;
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fprintf(stderr, "\033[93mSyntax Error: %s\033[0m\n", msg);
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}
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%}
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// define a reentrant parser
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%define api.pure
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// enable parser tracing and detailed error messages (plus Lookahead Correction)
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%define parse.trace
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%define parse.error detailed
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%define parse.lac full
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%lex-param { yyscan_t scanner }
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%parse-param { struct parser_state* state }
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%parse-param { yyscan_t scanner }
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%union {
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unsigned long num;
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}
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%start input
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%token NEWLINE
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%token <num> NUM
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%term END_OF_FILE
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%%
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input
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: treerow input
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| END_OF_FILE { return 0; }
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;
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treerow
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: NUM treerow {
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if (state->pos >= state->allocated) {
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state->allocated += 10;
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state->current_line = realloc(state->current_line, state->allocated * sizeof(unsigned short));
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if (!state->current_line) {
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fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
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YYABORT;
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}
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}
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state->current_line[state->pos] = $1;
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state->pos++;
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}
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| NEWLINE {
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if (state->pos != 0) {
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state->forest = realloc(state->forest, (state->rows + 1) * sizeof(unsigned short *));
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if (!state->forest) {
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fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
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YYABORT;
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}
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// resize the current line if necessary
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if (state->allocated > state->pos) {
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state->current_line = realloc(state->current_line, state->pos * sizeof(unsigned short));
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// cannot really fail but oh well
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if (!state->current_line) {
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fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
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YYABORT;
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}
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}
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if (state->pos != state->cols) {
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if (state->cols != 0) {
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fprintf(stderr, "\033[91m[error] Column size has changed mid-parse\033[0m\n");
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YYERROR;
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}
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state->cols = state->pos;
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}
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// write the current line to the forest
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state->forest[state->rows] = state->current_line;
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state->rows++;
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// initialize a new row
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state->allocated = state->cols;
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state->pos = 0;
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state->current_line = calloc(state->allocated, sizeof(unsigned short));
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if (!state->current_line) {
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fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
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YYABORT;
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}
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}
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}
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;
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%%
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unsigned long compute_scenic_score(struct parser_state *state, size_t row, size_t col) {
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unsigned short height = state->forest[row][col];
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unsigned long up = 0;
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for (int r = row - 1; r >= 0; r--) {
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up++;
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if (state->forest[r][col] >= height) {
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break;
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}
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}
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unsigned long down = 0;
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for (size_t r = row + 1; r < state->rows; r++) {
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down++;
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if (state->forest[r][col] >= height) {
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break;
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}
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}
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unsigned long left = 0;
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for (int c = col - 1; c >= 0; c--) {
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left++;
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if (state->forest[row][c] >= height) {
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break;
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}
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}
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unsigned long right = 0;
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for (size_t c = col + 1; c < state->cols; c++) {
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right++;
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if (state->forest[row][c] >= height) {
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break;
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}
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}
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return up * down * left * right;
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}
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int main(void) {
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struct parser_state *state = calloc(1, sizeof(struct parser_state));
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if (!state) {
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fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
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return EXIT_FAILURE;
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}
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state->allocated = 100;
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state->current_line = calloc(state->allocated, sizeof(unsigned short));
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if (!state->current_line) {
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fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
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return EXIT_FAILURE;
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}
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yyscan_t scanner;
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if (yylex_init(&scanner)) {
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fprintf(stderr, "\033[91m[error] Could not initialize lexer\033[0m\n");
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return EXIT_FAILURE;
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}
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if (yyparse(state, scanner)) {
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// TODO: Error handling https://www.gnu.org/software/bison/manual/html_node/Parser-Function.html
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// error during parse occured
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return EXIT_FAILURE;
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}
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yylex_destroy(scanner);
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// task 1
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// create a bitmap marking counted visible trees
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bool **bitmap = calloc(state->rows, sizeof(bool *));
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if (!bitmap) {
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fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
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return EXIT_FAILURE;
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}
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for (size_t i = 0; i < state->rows; i++) {
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bitmap[i] = calloc(state->cols, sizeof(bool));
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if (!bitmap[i]) {
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fprintf(stderr, "\033[91m[error] Ran out of memory\033[0m\n");
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return EXIT_FAILURE;
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}
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}
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// count all outer rows and cols as visible
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unsigned long visible = 0;
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for (size_t c = 0; c < state->cols; c++) {
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unsigned short tallest = state->forest[0][c];
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bitmap[0][c] = true;
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visible++;
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// top->down
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for (size_t r = 0; r < (state->rows - 1); r++) {
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if (state->forest[r][c] > tallest) {
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tallest = state->forest[r][c];
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if (!bitmap[r][c]) {
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visible++;
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bitmap[r][c] = true;
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}
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}
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}
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// bottom->up
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tallest = state->forest[state->rows - 1][c];
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visible++;
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bitmap[state->rows - 1][c] = true;
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for (size_t r = state->rows - 1; r > 0; r--) {
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if (state->forest[r][c] > tallest) {
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tallest = state->forest[r][c];
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if (!bitmap[r][c]) {
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visible++;
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bitmap[r][c] = true;
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}
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}
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}
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}
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// move through individual rows
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for (size_t r = 0; r < state->rows; r++) {
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unsigned short tallest = state->forest[r][0];
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if (!bitmap[r][0]) {
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bitmap[r][0] = true;
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visible++;
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}
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// left->right
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for (size_t c = 0; c < (state->cols - 1); c++) {
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if (state->forest[r][c] > tallest) {
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tallest = state->forest[r][c];
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if (!bitmap[r][c]) {
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visible++;
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bitmap[r][c] = true;
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}
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}
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}
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// right->left
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tallest = state->forest[r][state->cols - 1];
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if (!bitmap[r][state->cols - 1]) {
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bitmap[r][state->cols - 1] = true;
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visible++;
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}
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for (size_t c = state->cols - 1; c > 0; c--) {
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if (state->forest[r][c] > tallest) {
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tallest = state->forest[r][c];
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if (!bitmap[r][c]) {
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visible++;
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bitmap[r][c] = true;
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}
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}
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}
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}
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printf("Visible trees: %zu\n", visible);
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unsigned long best = 0;
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for (size_t r = 0; r < state->rows; r++) {
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for (size_t c = 0; c < state->cols; c++) {
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unsigned long tmp = compute_scenic_score(state, r, c);
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if (tmp > best) {
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best = tmp;
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}
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}
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}
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printf("Best scenic score: %zu\n", best);
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return 0;
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}
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