Reverse Words in a String

Given a sentence, reverse the order of its words without affecting the order of letters within a given word.

Given a sentence, reverse the order of its words without affecting the order of letters within a given word.

Constraints

• Sentence contains English uppercase and lowercase letters, digits, and spaces.
• 1 ≤ sentence.length ≤ 10⁴
• The order of the letters within a word is not to be reversed.

Note: The input string may contain leading or trailing spaces or multiple spaces between words. The returned string, however, should only have a single space separating each word. Do not include any extra spaces.

Examples

Example 1

Input String: "Hello Friend" Reversed String: "Friend Hello"

Example 2

Input String: "Welcome to Educative" Reversed String: "Educative to Welcome"

Example 3

Input String: "Hurray 3 2 1" Reversed String: "1 2 3 Hurray"

Solution

Simple Two pointer approach convert this number into array and reverse this array .

function reverseWord(str) {
    const arr = str.split(' ').filter(word => word.length > 0);
    let left = 0;
    let right = arr.length - 1;
    while (left <= right) {
        [arr[left], arr[right]] = [arr[right], arr[left]];
        left++;
        right--;
    }
    return arr.join(' ');
}

console.log(reverseWord('Hello Friend'));           // "Friend Hello"
console.log(reverseWord('  Hello   Friend  '));      // "Friend Hello"
console.log(reverseWord('  a good   example '));     // "example good a"

Time complexity: O(N) Space Complexity: O(1)