Add solution #471

Author: JoshCrozier

README.md

@@ -459,6 +459,7 @@
 468|[Validate IP Address](./solutions/0468-validate-ip-address.js)|Medium|
 469|[Convex Polygon](./solutions/0469-convex-polygon.js)|Medium|
 470|[Implement Rand10() Using Rand7()](./solutions/0470-implement-rand10-using-rand7.js)|Medium|
+471|[Encode String with Shortest Length](./solutions/0471-encode-string-with-shortest-length.js)|Hard|
 472|[Concatenated Words](./solutions/0472-concatenated-words.js)|Hard|
 473|[Matchsticks to Square](./solutions/0473-matchsticks-to-square.js)|Medium|
 474|[Ones and Zeroes](./solutions/0474-ones-and-zeroes.js)|Medium|

solutions/0471-encode-string-with-shortest-length.js

@@ -0,0 +1,65 @@
+/**
+ * 471. Encode String with Shortest Length
+ * https://leetcode.com/problems/encode-string-with-shortest-length/
+ * Difficulty: Hard
+ *
+ * Given a string s, encode the string such that its encoded length is the shortest.
+ *
+ * The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets
+ * is being repeated exactly k times. k should be a positive integer.
+ *
+ * If an encoding process does not make the string shorter, then do not encode it. If there are
+ * several solutions, return any of them.
+ */
+
+/**
+ * @param {string} s
+ * @return {string}
+ */
+var encode = function(s) {
+  const n = s.length;
+  const dp = Array.from({ length: n }, () => new Array(n).fill(''));
+
+  for (let len = 1; len <= n; len++) {
+    for (let start = 0; start + len <= n; start++) {
+      const end = start + len - 1;
+      const substr = s.slice(start, end + 1);
+
+      dp[start][end] = substr;
+
+      for (let k = 1; k < len; k++) {
+        const left = dp[start][start + k - 1];
+        const right = dp[start + k][end];
+        const combined = left + right;
+        if (combined.length < dp[start][end].length) {
+          dp[start][end] = combined;
+        }
+      }
+
+      let repeat = 1;
+      const patternLen = len;
+      while (repeat * patternLen <= n && s.slice(start, start + patternLen).repeat(repeat)
+        === s.slice(start, start + repeat * patternLen)) {
+        const encoded = `${repeat}[${dp[start][start + patternLen - 1]}]`;
+        if (encoded.length < dp[start][end].length) {
+          dp[start][end] = encoded;
+        }
+        repeat++;
+      }
+
+      for (let k = 1; k < len; k++) {
+        if (len % k === 0) {
+          const pattern = s.slice(start, start + k);
+          if (pattern.repeat(len / k) === substr) {
+            const encoded = `${len / k}[${dp[start][start + k - 1]}]`;
+            if (encoded.length < dp[start][end].length) {
+              dp[start][end] = encoded;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  return dp[0][n - 1];
+};