AOC 2020: Solution for day 10

Author: mbeaudoin

2020/day_10/Makefile

@@ -36,7 +36,6 @@ run: getdata puzzle
 	./puzzle $(INPUT_DATAFILE)
 
 getdata:
-	cp ../template/template_main.cpp ./puzzle.cpp
 	@echo "Getting data for day # $(DAY_NUM)"
 	test -f $(INPUT_DATAFILE) || $(WGET) $(WGET_ARGS) -O $(INPUT_DATAFILE) $(AOC_INPUT_URL)
 clean:

2020/day_10/puzzle.cpp

@@ -0,0 +1,177 @@
+//
+// Copyright (C) Martin Beaudoin. 2020. All Rights Reserved.
+//
+// See the repository's LICENSE file for the full license details.
+//
+
+#include <iostream>
+#include <cassert>
+#include <vector>
+#include <numeric>      // std::adjacent_difference
+#include <algorithm>    // std::adjacent_find
+#include "myutils.h"
+
+using namespace std;
+
+// Solve puzzle #1
+template <typename T>
+constexpr int solve_puzzle1(T data)
+{
+    int nbrDiff1 = 1;  // accounting for charging outlet
+    int nbrDiff3 = 1;  // accounting for device builtin adapter
+    std::sort(data.begin(), data.end());
+
+    //cout << " Puzzle #1:" << endl;
+
+    for(auto i = data.begin(); i < data.end() - 1; i++)
+    {
+        //cout << *i << ":" << *(i+1) << ":" << *(i+1) - *i << endl;
+
+        nbrDiff1 += (*(i+1) - *i == 1);
+        nbrDiff3 += (*(i+1) - *i == 3);
+    }
+
+    return nbrDiff1 * nbrDiff3;
+}
+
+long sumOfConsecutiveNumbers(int n)
+{
+    long sum=0;
+    for(int i=1; i<=n; i++)
+        sum += i;
+
+    return sum;
+}
+// Solve puzzle #2
+template <typename T>
+unsigned long solve_puzzle2(T data)
+{
+    unsigned long nbrCombinations = 0;
+    // Add the charging outlet
+    data.push_back(0);
+
+    // Add the device builtin adapter
+    data.push_back(*max_element(data.begin(), data.end()) + 3);
+
+    std::sort(data.begin(), data.end());
+
+    // Find blocks of +1 deltas
+    vector<int> diff(data.size());
+    std::adjacent_difference (data.begin(), data.end(), diff.begin());
+
+    // We can remove at most 2 out of a group of n consecutive delta1
+
+    // Compute the length of blocks of delta1
+    int blockLength = 0;
+    for(auto d = diff.begin(); d < diff.end() - 1; d++)
+    {
+        if(*d == 1 && *(d+1) == 1)
+        {
+            blockLength++;
+        }
+        else
+        {
+            // We have a block of delta1
+            if(blockLength > 0)
+            {
+                // The number of possible combinations is the sum of [1..'blockLength'] numbers
+                // plus 1 (the original unmodified sequence)
+                int blockCombinations = sumOfConsecutiveNumbers(blockLength) + 1;
+
+                if(nbrCombinations == 0)
+                    nbrCombinations += blockCombinations;
+                else
+                    nbrCombinations *= blockCombinations;
+
+                // Reset for next block
+                blockLength = 0;
+            }
+        }
+    }
+    return nbrCombinations;
+}
+
+int main(int argc, char *argv[])
+{
+    // Need a command-line parameter for the input filename
+    if (argc != 2) {
+        cerr << "Error: missing input" << endl;
+        return EXIT_FAILURE;
+    }
+
+    string filename(argv[1]);
+
+    // This file needs to exist
+    if (! myutils::file_exists(filename))
+    {
+        cerr << "Error: nonexistent file: " << filename << endl;
+        return EXIT_FAILURE;
+    }
+
+    // Reading the data
+    vector<int> data;
+    myutils::read_file<int, vector<int>>(data, filename, true, false);
+
+    // --------- Puzzle #1 ---------
+    // Verify puzzle1 examples
+    vector<int>example1 = {
+        16,
+        10,
+        15,
+        5,
+        1,
+        11,
+        7,
+        19,
+        6,
+        12,
+        4};
+
+    vector<int>example2 = {
+        28,
+        33,
+        18,
+        42,
+        31,
+        14,
+        46,
+        20,
+        48,
+        47,
+        24,
+        23,
+        49,
+        45,
+        19,
+        38,
+        39,
+        11,
+        1,
+        32,
+        25,
+        35,
+        8,
+        17,
+        7,
+        9,
+        4,
+        2,
+        34,
+        10,
+        3
+    };
+
+    assert(solve_puzzle1<vector<int>>(example1) == 35 && "Error verifying puzzle #1");
+    assert(solve_puzzle1<vector<int>>(example2) == 220 && "Error verifying puzzle #1");
+
+    // Solve puzzle #1
+    std::cout << "Answer for puzzle #1: "<< solve_puzzle1(data) << std::endl;
+
+    // --------- Puzzle #2 ---------
+    // Verify puzzle2 examples
+    assert(solve_puzzle2<vector<int>>(example1) == 8 && "Error verifying puzzle #2 with example1");
+    assert(solve_puzzle2<vector<int>>(example2) == 19208 && "Error verifying puzzle #2 with example2");
+
+    // Solve puzzle #2
+    std::cout << "Answer for puzzle #2: "<< solve_puzzle2(data) << std::endl;
+}

2020/day_11/Makefile

@@ -36,7 +36,6 @@ run: getdata puzzle
 	./puzzle $(INPUT_DATAFILE)
 
 getdata:
-	cp ../template/template_main.cpp ./puzzle.cpp
 	@echo "Getting data for day # $(DAY_NUM)"
 	test -f $(INPUT_DATAFILE) || $(WGET) $(WGET_ARGS) -O $(INPUT_DATAFILE) $(AOC_INPUT_URL)
 clean: