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LearnTwo Pointers

Valid Palindrome

Read the lesson → understand the pattern → then code. Tutor works offline (built-in teacher); optional Cursor/Gemini keys upgrade chat quality.

Topic refresher: Two Pointers — Two Indices, One Rule

Move left/right based on a condition instead of checking all pairs.

int L = 0, R = n - 1;
while (L < R) {
    int sum = a[L] + a[R];
    if (sum == target) { L++; R--; }
    else if (sum < target) L++;
    else R--;
}
Two Pointers

Valid Palindrome

Easy
LeetCode
1/7
EasyTwo PointersLeetCode #125

Valid Palindrome

Two pointers from ends. Skip non-alnum. Compare lowercased.

Examples

Example 1

Input

A man, a plan, a canal: Panama

Output

true
Example 2

Input

race a car

Output

false

Stuck? Take a nudge

C++17