Add 2020 day 1,2,3

2020/day1/day1.js

@@ -0,0 +1,24 @@
+#!/bin/node
+
+const fs = require('fs');
+
+fs.readFile('input.txt', (err, data) => {
+    const numbers = data.toString().split('\n').map(n => parseInt(n));
+    for (let i = 0; i < numbers.length; i++) {
+        for (let j = i + 1; j < numbers.length; j++) {
+            if (numbers[i] + numbers[j] === 2020) {
+                console.log(numbers[i] * numbers[j]);
+            }
+        }
+    }
+
+    for (let i = 0; i < numbers.length; i++) {
+        for (let j = i + 1; j < numbers.length; j++) {
+            for (let k = j + 1; k < numbers.length; k++) {
+                if (numbers[i] + numbers[j] + numbers[k] === 2020) {
+                    console.log(numbers[i] * numbers[j] * numbers[k]);
+                }
+            }
+        }
+    }
+});

2020/day2/day2.js

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+#!/bin/node
+
+const fs = require('fs');
+
+fs.readFile('input.txt', (err, data) => {
+    const passwords = data.toString().split('\n').filter(l => l.length > 0);
+    let q1 = 0, q2 = 0;
+
+    for (const [format, password] of passwords.map(line => line.split(':'))) {
+        const [occurrences, letter] = format.split(' ');
+        const [min, max] = occurrences.split('-').map(n => parseInt(n));
+
+        console.log(min, max, letter, password);
+
+        // q1
+        let count = 0;
+        for (let j = 0; j < password.length; j++) {
+            if (password[j] === letter) {
+                count++;
+            }
+        }
+        if (count >= min && count <= max) q1++;
+
+        // q2
+        if (password[min] === letter && password[max] !== letter || password[min] !== letter && password[max] === letter) q2++;
+    }
+
+    console.log(q1, q2);
+});

2020/day3/day3.js

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+#!/bin/node
+
+const fs = require('fs');
+
+fs.readFile('input.txt', (err, data) => {
+    const lines = data.toString().split('\n').filter(l => l.length > 0);
+    width = lines[0].length;
+
+    const slopes = [
+        [1, 1],
+        [3, 1],
+        [5, 1],
+        [7, 1],
+        [1, 2],
+    ];
+    const positions = slopes.map(_ => 0);
+    const results = slopes.map(_ => 0);
+	
+    for (let i = 0; i < lines.length; i++) {
+        const line = lines[i];
+
+        for (let j = 0; j < slopes.length; j++) {
+            const [right, down] = slopes[j];
+
+            if (i % down === 0) {
+                if (line[positions[j]] === '#') results[j]++;
+
+                positions[j] = (positions[j] + right) % width;
+            }
+        }
+    }
+
+    console.log(results, results.reduce((a, n) => a * n, 1));
+});