Runtime: 111 ms (Top 16.6%) | Memory: 50.12 MB (Top 33.3%)

Author: AnasImloul

scripts/algorithms/S/Special Binary String/Special Binary String.js

@@ -1,17 +1,50 @@
-var makeLargestSpecial = function(s) {
-  return recurse(s);
-  
-  function recurse(s) {
-    let i = 0, res = [], bal = 0;
-    for (let j = 0; j < s.length; j++) {
-      if (s[j] === '1') bal++;
-      else bal--;
-      if (bal === 0) { // found a balanced special substring
-        res.push('1' + recurse(s.slice(i + 1, j)) + '0'); // s[i] must be 1 and s[j] must be 0, if 1...1, it would be invalid.
-        i = j + 1; // go to next start position
+// Runtime: 111 ms (Top 16.6%) | Memory: 50.12 MB (Top 33.3%)
+
+/**
+ * @param {string} S
+ * @return {string}
+ */
+var makeLargestSpecial = function (S) {
+  let t = S
+  while (true) {
+    let t1 = largest(t)
+    if (t1 == t) return t
+    t = t1
+  }
+  function largest(S) {
+    let arr = S.split('').map(x => Number.parseInt(x)),
+      num = Number.parseInt(S, 2), rtn = S
+    for (let firstEndIndex = 1; firstEndIndex < S.length - 2; firstEndIndex++) {
+      for (let lLength = 2; lLength < firstEndIndex + 2; lLength += 2) {
+        let firstStartIndex = firstEndIndex - lLength + 1
+        if (!isSpecial(firstStartIndex, firstEndIndex)) continue
+        for (let rLength = 2; rLength < S.length - firstEndIndex; rLength += 2) {
+          let secondStartIndex = firstEndIndex + 1, secondEndIndex = firstEndIndex + rLength
+          if (!isSpecial(secondStartIndex, secondEndIndex)) continue
+          let str = [...arr.slice(0, firstStartIndex),
+          ...arr.slice(secondStartIndex, secondEndIndex + 1),
+          ...arr.slice(firstStartIndex, firstEndIndex + 1),
+          ...arr.slice(secondEndIndex + 1)].join('')
+          let newNum = Number.parseInt(str, 2)
+          if (newNum > num) {
+            num = newNum
+            rtn = str
+          }
+        }
+      }
+    }
+    return rtn
+
+    function isSpecial(start, end) {
+      let t = 0
+      for (let i = start; i <= end; i++) {
+        t += arr[i] == 1 ? 1 : -1
+        if (t < 0) return false // this is the second rule, really bad description
       }
+      return t == 0 ? true : false
     }
-    res.sort((a, b) => b.localeCompare(a)); // sort substrings in desc order
-    return res.join(""); 
   }
+
 };
+
+// console.log(makeLargestSpecial("101101011000"))