Reverse a String

Solved

Difficulty: Basic Accuracy: — Submissions: 0 Points: 1

Given a string s, return the string with its characters in reverse order.

Examples:

Input: s = "hello"

Output: "olleh"

Explanation: Reading the characters from the end gives olleh.

Input: s = "w3colleges"

Output: "segelloc3w"

Constraints:

1 ≤ s.length ≤ 10^5
s contains printable ASCII characters without spaces

Expected Complexities

Time Complexity: O(n) Auxiliary Space: O(1)

Company Tags

Infosys TCS

Topic Tags

Basic Strings

Swap the first and last characters, then the second and second-last, and keep moving inwards until the two pointers meet. That is n/2 swaps and no extra memory. In Python the slice s[::-1] does the same thing in one expression.

char *reverseString(char *s) {
    int i = 0, j = strlen(s) - 1;
    while (i < j) {
        char t = s[i];
        s[i++] = s[j];
        s[j--] = t;
    }
    return s;
}