Reverse a String

Easy · rating 950 · strings, implementation

Read a single line and print it reversed.

For input hello, print olleh.

Editorial

Approach

Swap characters from the two ends toward the middle with two pointers, or use your language's built-in reverse. The two-pointer version reverses in place with no extra allocation.

i, j = 0, len(s) - 1
while i < j:
    s[i], s[j] = s[j], s[i]
    i, j = i + 1, j - 1

Complexity

Time: O(n). Space: O(1) in place.

Open Reverse a String in Code Arena →