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Reverse String

Easy

Swap the ends, walk inward

In simple words

Swap the first and last letters, then move inward — like flipping a word end to end.

The idea

Reverse in place with two pointers: swap the first and last characters, then move both toward the middle until they meet.

L
R
a
l
g
o
v
i
z
0
1
2
3
4
5
6

Step 1 of 5. Swap the ends and walk inward — reverses the string in place. Values: a, l, g, o, v, i, z. Pointers: L at index 0, R at index 6.

1/5
Optimal
timeO(n)spaceO(1)

In-place end swaps.

1// swap the ends, walk inward2let l = 0, r = s.length - 1;3while (l < r) {4  [s[l], s[r]] = [s[r], s[l]];5  l++; r--;6}7return s;

Input

array
[a, l, g, o, v, i, z]

Memory

L
= 0 [a]
R
= 6 [z]

Output

result
—

Check yourself

3 quick questions about this walkthrough. A wrong answer costs nothing.

Examples

Example 1

Input:
s = "hello"
Output:
"olleh"
Explanation:
Swap ends inward.

Example 2

Input:
s = "a"
Output:
"a"
Explanation:
One letter.

Example 3

Input:
s = "ab"
Output:
"ba"
Explanation:
Two letters swap.

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