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🔥
7 Day Streak
✅
23 Solved Total
⚡
2,450 Total XP
🏆
#142 Global Rank
Today's Challenge
Live Now · Resets in 14:32:09

Longest Substring Without Repeating Characters

● Medium 🐍 Python  /  ⚡ JS  /  ☕ Java 👁 3,421 attempts today

Given a string s, find the length of the longest substring without repeating characters. Can you solve it in O(n) time?

+150 XP
Bonus reward
Attempt Now
Streak bonus: ×1.5 XP
Your Progress
Easy Solved
14 / 48
Medium Solved
7 / 62
Hard Solved
2 / 30
Acceptance Rate
61%

Problem Set

Browse all 140 →
Easy Arrays
+50 XP
#1 · Two Sum
Find two numbers in an array that add up to a given target. The classic hash map solution.
👁 89k ✅ 72%
Review ↗
Medium Strings
+100 XP
#3 · Longest Substring
Sliding window approach to find the longest substring without repeating characters.
👁 61k ✅ 55%
Review ↗
Medium Arrays
+100 XP
#11 · Container With Most Water
Two-pointer technique to maximize the amount of water a container can hold.
👁 47k ✅ 58%
Solve →
Easy DP
+50 XP
#70 · Climbing Stairs
Classic intro to dynamic programming. Count distinct ways to climb n stairs taking 1 or 2 steps.
👁 72k ✅ 80%
Solve →
Medium Trees
+100 XP
#102 · Binary Tree Level Order
BFS traversal to return values of nodes level by level, left to right.
👁 38k ✅ 67%
Solve →
Hard Graphs
+250 XP
#127 · Word Ladder
BFS on an implicit graph. Transform one word to another by changing one letter at a time.
👁 29k ✅ 38%
Solve →
Hard DP
+250 XP
#72 · Edit Distance
2D DP to compute the minimum operations to convert one word to another. Levenshtein distance.
👁 19k ✅ 42%
Solve →
Easy Strings
+50 XP
#14 · Longest Common Prefix
Find the longest common prefix string among an array of strings. Vertical scanning.
👁 55k ✅ 76%
Solve →
Hard Arrays
+250 XP
#42 · Trapping Rain Water
Classic two-pointer problem. Compute how much water can be trapped between elevation bars.
👁 44k ✅ 45%
Solve →

🏆 Top Solvers

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WA
Walter A.
82 solved 🔥21 9,200 XP
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SJ
Sarah J.
79 solved 🔥18 8,750 XP
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BD
Brandon D.
71 solved 🔥15 7,400 XP
4
AJ
Amanda J.
65 solved 🔥12 6,800 XP
5
JP
Joseph P.
60 solved 🔥9 6,100 XP
#142
You
You
23 solved 🔥7 2,450 XP
⚡ XP Guide
Easy problem +50 XP
Medium problem +100 XP
Hard problem +250 XP
Daily challenge +150 XP
Streak bonus (7d) ×1.5 XP
First solve (new) +25 Bonus
Competitions

Weekly Contests

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APR
26
Weekly Contest #47 — Algorithms Sprint
🕖 Saturday, 8:00 PM IST ⏱ 90 minutes 👥 4 problems 🧑‍💻 312 registered
🥇 3,000 XP 🥈 1,500 XP 🥉 750 XP Top 10 · Certificate
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MAY
03
Biweekly Contest #24 — DP & Graph Special
🕖 Saturday, 8:00 PM IST ⏱ 90 minutes 👥 5 problems 🧑‍💻 189 registered
🥇 5,000 XP 🥈 2,500 XP 🥉 1,000 XP Top 5 · 1 Free Month Pro
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MAY
10
Monthly Grand Prix — Full Stack Showdown
🕖 Saturday, 7:00 PM IST ⏱ 3 hours 👥 Build a feature 🧑‍💻 78 registered
🥇 ₹10,000 Cash 🥈 ₹5,000 Cash 🥉 6-Month Pro Top 3 · Mentorship Session
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