feat(euler): 17 - Number letter counts

-

challenges/euler/readme.md

@@ -28,7 +28,7 @@ The source code can be found in the [src](src) directory. My thoughts about some
 -   [x] [15 - Lattice paths](src/15%20-%20Lattice%20paths.ts)
     -   [Thoughts](thoughts/15%20-%20Lattice%20paths.md)
 -   [x] [16 - Power digit sum](src/16%20-%20Power%20digit%20sum.ts)
--   [ ] 17 - Number letter counts
+-   [x] [17 - Number letter counts](src/17%20-%20Number%20letter%20counts.ts)
 -   [ ] 18 - Maximum path sum I
 -   [ ] 19 - Counting Sundays
 -   [ ] 20 - Factorial digit sum

challenges/euler/src/17 - Number letter counts.ts

@@ -0,0 +1,82 @@
+export {};
+
+const translations = {
+    1: 'one',
+    2: 'two',
+    3: 'three',
+    4: 'four',
+    5: 'five',
+    6: 'six',
+    7: 'seven',
+    8: 'eight',
+    9: 'nine',
+    10: 'ten',
+    11: 'eleven',
+    12: 'twelve',
+    13: 'thirteen',
+    14: 'fourteen',
+    15: 'fifteen',
+    16: 'sixteen',
+    17: 'seventeen',
+    18: 'eighteen',
+    19: 'nineteen',
+    20: 'twenty',
+    30: 'thirty',
+    40: 'forty',
+    50: 'fifty',
+    60: 'sixty',
+    70: 'seventy',
+    80: 'eighty',
+    90: 'ninety'
+};
+
+// works for what we need, could be improved
+const numberToWords = (n: number): string => {
+    let out = '';
+
+    // Deal with thousands
+    const thousands = Math.floor(n / 1000);
+
+    if (thousands > 0) {
+        for (let i = 0; i < thousands; i++) n -= 1000;
+        out += `${translations[thousands]} thousand`;
+    }
+
+    // Deal with hundreds
+    const hundreds = Math.floor(n / 100);
+
+    if (hundreds > 0) {
+        for (let i = 0; i < hundreds; i++) n -= 100;
+        out += `${translations[hundreds]} hundred`;
+    }
+
+    // Deal with tens
+    const tens = Math.floor(n / 10);
+
+    if (tens > 0) {
+        if (hundreds > 0) out += ' and ';
+        for (let i = 0; i < tens; i++) n -= 10;
+
+        if (n % 10 > 0 && tens == 1) {
+            out += `${translations[10 + (n % 10)]}`;
+            n -= n % 10;
+        } else out += `${translations[tens * 10]} `;
+    }
+
+    // Deal with the remainder
+    if (n > 0) {
+        if (hundreds > 0 && tens <= 0) out += ' and ';
+        out += translations[n];
+    }
+
+    return out;
+};
+
+let sum = 0;
+
+for (let i = 1; i <= 1000; i++) {
+    // Strip the words of all whitespace and add the length to the sum
+    sum += numberToWords(i).replace(/\s+/g, '').length;
+}
+
+console.log(sum);