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Concept

Introduction

Go deep, then backtrack · pre/in/post order
step 1 / 20
binary tree
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call stack ↓
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Concept
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1dfs(node):
2    if node is null: return
3    visit(node)          // PRE-order
4    dfs(node.left)       // IN-order sits between the two recursions
5    // (return / backtrack)
6    dfs(node.right)      // POST-order acts here, after both
state
  • strategygo deep, then backtrack

line 1Depth-First Search dives down one branch as far as it can go, then BACKTRACKS and tries the next branch. Contrast this with breadth-first, which sweeps level by level. Here we walk the same tree three different ways to reveal the three classic DFS orders.