Add solution #788

Author: JoshCrozier

README.md

@@ -598,6 +598,7 @@
 785|[Is Graph Bipartite?](./0785-is-graph-bipartite.js)|Medium|
 786|[K-th Smallest Prime Fraction](./0786-k-th-smallest-prime-fraction.js)|Medium|
 787|[Cheapest Flights Within K Stops](./0787-cheapest-flights-within-k-stops.js)|Medium|
+788|[Rotated Digits](./0788-rotated-digits.js)|Medium|
 790|[Domino and Tromino Tiling](./0790-domino-and-tromino-tiling.js)|Medium|
 791|[Custom Sort String](./0791-custom-sort-string.js)|Medium|
 796|[Rotate String](./0796-rotate-string.js)|Easy|

solutions/0788-rotated-digits.js

@@ -0,0 +1,50 @@
+/**
+ * 788. Rotated Digits
+ * https://leetcode.com/problems/rotated-digits/
+ * Difficulty: Medium
+ *
+ * An integer x is a good if after rotating each digit individually by 180 degrees, we get a valid
+ * number that is different from x. Each digit must be rotated - we cannot choose to leave it alone.
+ *
+ * A number is valid if each digit remains a digit after rotation. For example:
+ * - 0, 1, and 8 rotate to themselves,
+ * - 2 and 5 rotate to each other (in this case they are rotated in a different direction, in other
+ *   words, 2 or 5 gets mirrored),
+ * - 6 and 9 rotate to each other, and
+ * - the rest of the numbers do not rotate to any other number and become invalid.
+ *
+ * Given an integer n, return the number of good integers in the range [1, n].
+ */
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var rotatedDigits = function(n) {
+  let result = 0;
+
+  for (let i = 1; i <= n; i++) {
+    if (verify(i)) {
+      result++;
+    }
+  }
+
+  return result;
+
+  function verify(num) {
+    const digits = num.toString().split('');
+    let result = false;
+
+    for (const digit of digits) {
+      if (digit === '3' || digit === '4' || digit === '7') {
+        return false;
+      }
+
+      if (digit === '2' || digit === '5' || digit === '6' || digit === '9') {
+        result = true;
+      }
+    }
+
+    return result;
+  }
+};