|435|[Non-overlapping Intervals](https://leetcode.com/problems/non-overlapping-intervals/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_435.java) | |Medium| Greedy

|434|[Number of Segments in a String](https://leetcode.com/problems/number-of-segments-in-a-string/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_434.java)||Easy|

|432|[All O`one Data Structure](https://leetcode.com/problems/all-oone-data-structure/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_432.java)| |Hard| Design

|430|[Flatten a Multilevel Doubly Linked List](https://leetcode.com/problems/flatten-a-multilevel-doubly-linked-list/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_430.java)| |Medium|LinkedList, DFS, Doubly-Linked List

|429|[N-ary Tree Level Order Traversal](https://leetcode.com/problems/n-ary-tree-level-order-traversal/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_429.java)| |Easy| BFS, Tree

|425|[Word Squares](https://leetcode.com/problems/word-squares/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_425.java)| |Hard| Trie, Backtracking, Recursion

|424|[Longest Repeating Character Replacement](https://leetcode.com/problems/longest-repeating-character-replacement/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_424.java)| | Medium| Sliding Window

packagecom.fishercoder.solutions;

publicclass_430 {

publicstaticclassSolution1 {

publicNodeflatten(Nodehead) {

if (head ==null) {

returnnull;

}

Nodepre =newNode(-1,null,head,null);

dfs(pre,head);

pre.next.prev =null;

returnpre.next;

}

privateNodedfs(Nodeprev,Nodecurr) {

if (curr ==null) {

returnprev;

}

curr.prev =prev;

prev.next =curr;

Nodenext =curr.next;

Nodetail =dfs(curr,curr.child);

curr.child =null;

returndfs(tail,next);

}

}

publicstaticclassNode {

publicintval;

publicNodeprev;

publicNodenext;

publicNodechild;

publicNode(intval,Nodeprev,Nodenext,Nodechild) {

this.val =val;

this.prev =prev;

this.next =next;

this.child =child;

}

}

}