993.Cousins in Binary Tree
EasyBinary TreeBreadth-First SearchDepth-First Search59.8% acceptance6 companiesVideo
With video · 318 results
1020.Number of Enclaves
MediumArrayBreadth-First SearchDepth-First Search72.2% acceptance5 companiesVideo
1022.Sum of Root To Leaf Binary Numbers
EasyBinary TreeDepth-First SearchTree76.6% acceptance6 companiesVideo
1026.Maximum Difference Between Node and Ancestor
MediumBinary TreeDepth-First SearchTree78.1% acceptance5 companiesVideo
1028.Recover a Tree From Preorder Traversal
HardBinary TreeDepth-First SearchString83.2% acceptance6 companiesVideo
1034.Coloring A Border
MediumArrayBreadth-First SearchDepth-First Search51.8% acceptance3 companiesVideo
1036.Escape a Large Maze
HardArrayBreadth-First SearchDepth-First Search37.0% acceptance4 companiesVideo
1038.Binary Search Tree to Greater Sum Tree
MediumBinary Search TreeBinary TreeDepth-First Search88.3% acceptance3 companiesVideo
1042.Flower Planting With No Adjacent
MediumBreadth-First SearchDepth-First SearchGraph54.1% acceptance2 companiesVideo
1080.Insufficient Nodes in Root to Leaf Paths
MediumBinary TreeDepth-First SearchTree55.6% acceptance1 companyVideo
1102.Path With Maximum Minimum Value
MediumArrayBinary SearchBreadth-First Search54.6% acceptance3 companiesPremium elsewhere, free hereVideo
1110.Delete Nodes And Return Forest
MediumArrayBinary TreeDepth-First Search72.4% acceptance4 companiesVideo
1120.Maximum Average Subtree
MediumBinary TreeDepth-First SearchTree66.7% acceptance1 companyPremium elsewhere, free hereVideo
1123.Lowest Common Ancestor of Deepest Leaves
MediumBinary TreeBreadth-First SearchDepth-First Search79.5% acceptance4 companiesVideo
1145.Binary Tree Coloring Game
MediumBinary TreeDepth-First SearchTree52.9% acceptance2 companiesVideo
1161.Maximum Level Sum of a Binary Tree
MediumBinary TreeBreadth-First SearchDepth-First Search70.0% acceptance4 companiesVideo
1192.Critical Connections in a Network
HardBiconnected ComponentDepth-First SearchGraph60.6% acceptance8 companiesVideo
1202.Smallest String With Swaps
MediumArrayBreadth-First SearchDepth-First Search61.0% acceptance8 companiesVideo
1203.Sort Items by Groups Respecting Dependencies
HardBreadth-First SearchDepth-First SearchGraph66.0% acceptance5 companiesVideo
1214.Two Sum BSTs
MediumBinary SearchBinary Search TreeBinary Tree68.2% acceptance1 companyPremium elsewhere, free hereVideo
1233.Remove Sub-Folders from the Filesystem
MediumArrayDepth-First SearchString78.6% acceptance8 companiesVideo
1236.Web Crawler
MediumBreadth-First SearchDepth-First SearchInteractive68.8% acceptance7 companiesPremium elsewhere, free hereVideo
1245.Tree Diameter
MediumBreadth-First SearchDepth-First SearchGraph61.1% acceptance7 companiesPremium elsewhere, free hereVideo
1254.Number of Closed Islands
MediumArrayBreadth-First SearchDepth-First Search70.4% acceptance5 companiesVideo
1257.Smallest Common Region
MediumArrayBreadth-First SearchDepth-First Search68.6% acceptance1 companyPremium elsewhere, free hereVideo
1261.Find Elements in a Contaminated Binary Tree
MediumBinary TreeBreadth-First SearchDepth-First Search84.1% acceptance2 companiesVideo
1267.Count Servers that Communicate
MediumArrayBreadth-First SearchCounting73.5% acceptance6 companiesVideo
1273.Delete Tree Nodes
MediumArrayBreadth-First SearchDepth-First Search61.2% acceptance1 companyPremium elsewhere, free hereVideo
1302.Deepest Leaves Sum
MediumBinary TreeBreadth-First SearchDepth-First Search86.3% acceptance3 companiesVideo
1305.All Elements in Two Binary Search Trees
MediumBinary Search TreeBinary TreeDepth-First Search80.5% acceptance2 companiesVideo
1306.Jump Game III
MediumArrayBreadth-First SearchDepth-First Search70.1% acceptance3 companiesVideo
1315.Sum of Nodes with Even-Valued Grandparent
MediumBinary TreeBreadth-First SearchDepth-First Search85.6% acceptance4 companiesVideo
1319.Number of Operations to Make Network Connected
MediumBreadth-First SearchDepth-First SearchGraph67.0% acceptance10 companiesVideo
1325.Delete Leaves With a Given Value
MediumBinary TreeDepth-First SearchTree77.4% acceptance4 companiesVideo
1339.Maximum Product of Splitted Binary Tree
MediumBinary TreeDepth-First SearchTree55.7% acceptance5 companiesVideo
1361.Validate Binary Tree Nodes
MediumBinary TreeBreadth-First SearchDepth-First Search44.3% acceptance3 companiesVideo
1367.Linked List in Binary Tree
MediumBinary TreeDepth-First SearchLinked List52.1% acceptance5 companiesVideo
1372.Longest ZigZag Path in a Binary Tree
MediumBinary TreeDepth-First SearchDynamic Programming67.0% acceptance2 companiesVideo
1373.Maximum Sum BST in Binary Tree
HardBinary Search TreeBinary TreeDepth-First Search48.9% acceptance5 companiesVideo
1376.Time Needed to Inform All Employees
MediumBreadth-First SearchDepth-First SearchTree60.6% acceptance5 companiesVideo
1377.Frog Position After T Seconds
HardBreadth-First SearchDepth-First SearchGraph38.8% acceptance2 companiesVideo
1379.Find a Corresponding Node of a Binary Tree in a Clone of That Tree
EasyBinary TreeBreadth-First SearchDepth-First Search85.9% acceptance1 companyVideo
1382.Balance a Binary Search Tree
MediumBinary Search TreeBinary TreeDepth-First Search86.3% acceptance5 companiesVideo
1391.Check if There is a Valid Path in a Grid
MediumArrayBreadth-First SearchDepth-First Search64.5% acceptance3 companiesVideo
1430.Check If a String Is a Valid Sequence from Root to Leaves Path in a Binary Tree
MediumBinary TreeBreadth-First SearchDepth-First Search47.6% acceptancePremium elsewhere, free hereVideo
1443.Minimum Time to Collect All Apples in a Tree
MediumBreadth-First SearchDepth-First SearchHash Table63.6% acceptance4 companiesVideo
1448.Count Good Nodes in Binary Tree
MediumBinary TreeBreadth-First SearchDepth-First Search73.8% acceptance7 companiesVideo
1457.Pseudo-Palindromic Paths in a Binary Tree
MediumBinary TreeBit ManipulationBreadth-First Search68.3% acceptance2 companiesVideo
1462.Course Schedule IV
MediumBreadth-First SearchDepth-First SearchGraph60.4% acceptance6 companiesVideo
1466.Reorder Routes to Make All Paths Lead to the City Zero
MediumBreadth-First SearchDepth-First SearchGraph66.3% acceptance5 companiesVideo
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How to use these solutions
Each solution breaks the problem into approaches, usually from brute force to the best one, and explains why each works. Code comes in Python, Java, C++ and other languages. Knowing why an approach works matters more in an interview than remembering the code.
- Try the problem first. Give it at least 20 minutes before you open the solution.
- Read every approach. The brute force shows you the problem; the faster ones show the pattern.
- Check the complexity. Note the time and space of each approach and what makes the difference.
- Write it yourself. Close the solution and code it from memory in the editor.
- Come back in a week. Solving it again later is what makes the pattern stick.