“The difference between the hunter and the prey is persistence.”
- Sung Jin-Woo, moments before annihilating a dungeon boss
The Daily Quest: System Notification
Objective: Remove all occurrences of val from an array nums in-place.
Difficulty: 🟢 Level 2 (Beginner-Friendly But Tactical)
Reward: +15 DSA XP, +7 In-Place Operation Mastery
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The Problem: A Dungeon Infested with "Val" Monsters
Imagine your array is a dungeon corridor filled with monsters (elements equal to val). Your mission: eliminate them all without using extra space (no portals or shadow summons allowed).
Example:
Input: nums = [3, 2, 2, 3], val = 3 → Output: 2 (nums becomes [2, 2, _, _])
Constraints:
Do it in O(n) time.
Use O(1) memory (no creating new arrays).
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The Shadow Monarch’s Strategy: Two-Pointer Technique
Sung Jin-Woo doesn’t waste energy fighting every monster head-on. He strategically deploys his forces. Here’s how we mimicked his tactics:
- The Shadow Squad:
Scout (i): Traverses the dungeon (array) to identify threats.
Gatekeeper (k): Secures the safe zone by marking positions for non-monster elements.
- The Battle Plan:
Initialize k = 0 (Gatekeeper starts at the dungeon entrance).
Send the Scout (i) to inspect every element:
If nums[i] != val (not a monster), order the Gatekeeper to secure it at nums[k].
Advance the Gatekeeper (k++) to fortify the next position.
Return k (number of survivors).
Code Crafting: Commanding the Shadows
typescript
function removeElement(nums: number[], val: number): number {
let k = 0; // Gatekeeper starts at the gates
for (let i = 0; i < nums.length; i++) { // Scout explores the dungeon
if (nums[i] !== val) { // Found a human survivor!
nums[k] = nums[i]; // Gatekeeper secures them
k++; // Advance the safe zone
}
}
return k; // Total survivors
}
Live Battle Simulation:
Input: nums = [0, 1, 2, 2, 3, 0, 4, 2], val = 2
Scout (i=0): 0 is safe → Gatekeeper (k=0) secures it.
Scout (i=1): 1 is safe → Gatekeeper (k=1) secures it.
Scout (i=2): 2 is a monster → skipped.
Scout (i=6): 4 is safe → Gatekeeper (k=4) secures it.
Final Array: [0, 1, 3, 0, 4, _, _, _] → k = 5 survivors.
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Why This Strategy Dominates
Time Complexity: O(n) — Scout clears the dungeon in one sweep.
Space Complexity: O(1) — No mana (memory) wasted.
This is the coding equivalent of Sung Jin-Woo’s Shadow Extraction skill — efficient, ruthless, and resourceful.
Level-Up Loot (Key Takeaways)
In-Place Operations Are King: Like Jin-Woo repurposing defeated shadows, we repurposed the array itself.
Order Doesn’t Matter: Focus on securing survivors, not their sequence (chaos is acceptable in battle).
Edge Cases:
Empty dungeon (array)? Return 0.
All monsters (elements = val)? Return 0.
Join the Shadow Army (Community Callout)
Upvote if you’d partner with Sung Jin-Woo in this coding dungeon!
Comment Below:
Your favorite in-place algorithm tactic.
Which Solo Leveling character best represents recursion? (Beru? Igris?)
Post your solution — let’s see who writes the cleanest code!
“Those who hesitate are disqualified.” Keep grinding, hunters! 🔥
Follow My Journey:
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Series Tag: #SoloCodingJourney
“The System is watching. Are you strong enough to answer?” 🕶️