feat(leetcode): add No.1718

Author: mickey0524

1717.Maximum-Score-From-Removing-Substrings.java

@@ -1,6 +1,6 @@
 // https://leetcode.com/problems/maximum-score-from-removing-substrings/
 // algorithms
-// Easy (37.47%)
+// Medium (37.47%)
 // Total Accepted: 3,920
 // Total Submissions: 10,461
 

1718.Construct-the-Lexicographically-Largest-Valid-Sequence.java

@@ -0,0 +1,71 @@
+// https://leetcode.com/problems/construct-the-lexicographically-largest-valid-sequence/
+// algorithms
+// Medium (42.24%)
+// Total Accepted: 2,795
+// Total Submissions: 6,617
+
+
+class Solution {
+    
+    private static int[] res;
+    
+    private static boolean success;
+    
+    public int[] constructDistancedSequence(int n) {
+        res = new int[2 * n - 1];
+        success = false;
+        
+        recursive(0, n, new int[2 * n - 1], new HashSet<>());
+    
+        return res;
+    }
+    
+    private void recursive(int idx, int n, int[] tmp, Set<Integer> set) {
+        if (success) {
+            return;
+        }
+        
+        int len = res.length;
+        if (idx == len) {
+            for (int i = 0; i < len; i++) {
+                res[i] = tmp[i];
+            }
+            
+            success = true;
+            return;
+        }
+        
+        if (tmp[idx] != 0) {
+            recursive(idx + 1, n, tmp, set);
+            return;
+        }
+        
+        for (int i = n; i > 0; i--) {
+            if (set.contains(i)) {
+                continue;
+            }
+            if (i != 1 && (idx + i >= len || tmp[idx + i] != 0)) {
+                continue;
+            }
+            
+            tmp[idx] = i;
+            if (i != 1) {
+                tmp[idx + i] = i;
+            }
+            set.add(i);
+            
+            recursive(idx + 1, n, tmp, set);
+            
+            if (success) {
+                return;
+            }
+        
+            tmp[idx] = 0;
+            if (i != 1) {
+                tmp[idx + i] = 0;
+            }
+            set.remove(i);
+        }
+        
+    }
+}