MEDIUM Greedy
135. Candy
📖 Problem
There are n children standing in a line. Each child is assigned a rating value given in the integer array ratings. You are giving candies to these children subjected to the following requirements: - Each child must have at least one candy. - Children with a higher rating get more candies than their neighbors. Return the minimum number of candies you need to have to distribute the candies to the children.
🧠 Visual Learning Aid
1 Model the input into the right structure
2 Choose the core technique and invariant
3 Execute step-by-step with a sample
4 Validate complexity and edge cases
JS/TS Refreshers
- •Array methods (`push`, `pop`, `shift`, `slice`)
- •Object/Map/Set usage patterns
- •Function parameter and return typing
Logical Thinking Concepts
- •Define invariants before coding
- •Check edge cases first (`[]`, single element, duplicates)
- •Estimate time/space before implementation
- •Apply Greedy reasoning pattern
💡 Approach
- → Give each child 1 candy initially
- → Left to right pass: give more candy if rating > left neighbor
- → Right to left pass: give more candy if rating > right neighbor
- → Use max of both passes for each child
- → Time: O(n), Space: O(n)
🧭 Prerequisites
🛠️ Hints & Pitfalls
Hints
- •Give each child 1 candy initially
- •Left to right pass: give more candy if rating > left neighbor
- •Right to left pass: give more candy if rating > right neighbor
Common Pitfalls
- •Use max of both passes for each child
- •Time: O(n), Space: O(n)
🧪 Test Cases
Hidden tests on submit: 1
Test Case 1
Not run Input:
candy([1,0,2]); Expected:
5 Test Case 2
Not run Input:
candy([1,2,2]); Expected:
4 Test Case 3
Not run Input:
candy([1,3,2,2,1]); Expected:
7 📝 Code Editor
📤 Output