134 lines
2.7 KiB
C++
134 lines
2.7 KiB
C++
#include <fstream>
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#include <iostream>
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#include <sstream>
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#include <vector>
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using namespace std;
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long checksum(vector<long> blocks) {
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long sum = 0;
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for (long i = 0; i < blocks.size(); i++) {
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if (blocks[i] < 0) continue;
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sum += i * blocks[i];
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}
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return sum;
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}
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vector<long> parseDisk(const char *path) {
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ifstream input(path);
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string line;
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getline(input, line);
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char c;
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stringstream ss;
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ss << line;
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bool swap = true;
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// cout << line << endl;
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vector<long> blocks;
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long id = 0;
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while (ss >> c) {
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int num = c - '0';
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if (swap) {
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for (int i = 0; i < num; i++) {
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blocks.push_back(id);
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}
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id++;
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} else {
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for (int i = 0; i < num; i++) {
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blocks.push_back(-1);
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}
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}
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swap = !swap;
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}
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return blocks;
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}
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void printDisk(vector<long> blocks) {
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for (int i = 0; i < blocks.size(); i++) {
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if (blocks[i] < 0) {
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cout << '.';
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} else {
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cout << blocks[i];
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}
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}
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cout << endl;
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}
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long part1(const char* path) {
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vector<long> blocks = parseDisk(path);
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while (true) {
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bool flag = false;
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for (int i = 0; i < blocks.size(); i++) {
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if (blocks[i] == -1) {
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blocks[i] = blocks[blocks.size() - 1];
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blocks.pop_back();
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flag = true;
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break;
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}
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}
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if (!flag) break;
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}
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return checksum(blocks);
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}
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long part2(const char *path) {
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vector<long> blocks = parseDisk(path);
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// printDisk(blocks);
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int current_size = 1;
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long current_id = blocks[blocks.size() - 1];
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for (int i = blocks.size() - 2; i >= 0; i--) {
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if (blocks[i] == current_id) {
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current_size++;
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} else {
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// skip empty block
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if (current_id == -1) {
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current_size = 1;
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current_id = blocks[i];
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continue;
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}
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// try finding a new spot
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int empty_size = 0;
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for (int j = 0; j <= i + 1; j++) {
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// found empty spot
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if (empty_size >= current_size) {
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// cout << "empty_size=" << empty_size << " current_size=" << current_size << endl;
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for (int k = 0; k < current_size; k++) {
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blocks[j - k - 1] = current_id;
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blocks[i + 1 + k] = -1;
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}
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// printDisk(blocks);
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break;
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}
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// check for next empty spot
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if (blocks[j] == -1) {
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empty_size++;
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} else {
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empty_size = 0;
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}
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}
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current_size = 1;
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current_id = blocks[i];
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}
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}
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return checksum(blocks);
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}
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int main(int argc, char *argv[]) {
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cout << "example1: " << part1("example") << endl;
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cout << "input1: " << part1("input") << endl;
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cout << "example2: " << endl << part2("example") << endl;
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cout << "input2: " << part2("input") << endl;
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return 0;
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}
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