Create 1718-construct-the-lexicographically-largest-valid-sequence.js

Author: everthis

1718-construct-the-lexicographically-largest-valid-sequence.js

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+/**
+ * @param {number} n
+ * @return {number[]}
+ */
+const constructDistancedSequence = function(n) {
+  const ans = Array(2 * n - 1).fill(0)
+  const used = Array(n + 1).fill(0)
+  dfs(ans, 0)
+  return ans
+    
+  function dfs(ans, i) {
+    if(i === ans.length) return true
+    if(ans[i]) return dfs(ans, i + 1)
+    for(let j = used.length - 1; j > 0; j--) {
+      if(used[j]) continue
+      if(j !== 1 && (i + j >= ans.length || ans[i + j])) continue
+      used[j] = 1
+      ans[i] = j
+      if(j !== 1) ans[i + j] = j
+      if(dfs(ans, i + 1)) return true
+      ans[i] = 0
+      if(j !== 1) ans[i + j] = 0
+      used[j] = 0
+    }
+    return false
+  }
+};