Find Length of the Last Word

Problem Statement

Solution 1: Using String Methods

function getLengthOfLastWord(s) {
    if (typeof s !== 'string') throw new TypeError('Input must be a string');
    
    s = s.trim();
    const words = s.split(' ');
    return words[words.length - 1].length;
} 

const str1 = "hello aman";
getLengthOfLastWord(str1);  //output: 4 

Solution 2: Using Regular Expressions

function findLengthOfLastWordUsingRegex(s) {
    if (typeof s !== 'string') throw new TypeError('Input must be a string');
    
    const match = s.trim().match(/\S+$/);
    return match ? match[0].length : 0;
} 

const str1 = "hello aman";
findLengthOfLastWordUsingRegex(str1);  //output: 4 

Solution 3: Manual Traversal

function calculateLengthOfLastWord(s) {
    if (typeof s !== 'string') throw new TypeError('Input must be a string');
    
    let length = 0;
    let i = s.length - 1;

    while (i >= 0 && s[i] === ' ') {
        i--;
    }

    while (i >= 0 && s[i] !== ' ') {
        length++;
        i--;
    }

    return length;
} 

const str1 = "hello aman";
calculateLengthOfLastWord(str1);  //output: 4 

Solution 4: Using Array.prototype.reduce

function lengthOfLastWordWithReduce(s) {
    if (typeof s !== 'string') throw new TypeError('Input must be a string');
    
    return s.trim().split(/\s+/).reduce((_, word) => word.length, 0);
} 

const str1 = "hello aman";
lengthOfLastWordWithReduce(str1);  //output: 4 

Solution 5: Using Array.prototype.forEach

function lengthOfLastWordUsingForEach(s) {
    if (typeof s !== 'string') throw new TypeError('Input must be a string');
    
    let lastWordLength = 0;
    s.trim().split(/\s+/).forEach(word => lastWordLength = word.length);
    return lastWordLength;
} 

const str1 = "hello aman";
lengthOfLastWordUsingForEach(str1);  //output: 4 

Solution 6: Using Array.prototype.pop

function getLastWordLength(s) {
    if (typeof s !== 'string') throw new TypeError('Input must be a string');
    
    const words = s.trim().split(/\s+/);
    return words.pop().length;
} 

const str1 = "hello aman";
getLastWordLength(str1);  //output: 4 

Solution 7: Using String.prototype.lastIndexOf

function lengthOfLastWordWithLastIndexOf(s) {
    if (typeof s !== 'string') throw new TypeError('Input must be a string');
    
    s = s.trim();
    const lastSpace = s.lastIndexOf(' ');
    return s.length - lastSpace - 1;
} 

const str1 = "hello aman";
lengthOfLastWordWithLastIndexOf(str1);  //output: 4 

Solution 8: Using String.prototype.split with Map

function lengthOfLastWordUsingMap(s) {
    if (typeof s !== 'string') throw new TypeError('Input must be a string');
    
    const words = s.trim().split(/\s+/);
    return words.map(word => word.length).pop();
} 

const str1 = "hello aman";
lengthOfLastWordUsingMap(str1);  //output: 4 

Solution 9: Using Stack Approach

function lengthOfLastWordUsingStack(s) {
    if (typeof s !== 'string') throw new TypeError('Input must be a string');
    
    const stack = [];
    for (const char of s.trim()) {
        if (char === ' ') {
            stack.length = 0;
        } else {
            stack.push(char);
        }
    }
    return stack.length;
} 

const str1 = "hello aman";
lengthOfLastWordUsingStack(str1);  //output: 4 

Solution 10: Using String.prototype.substring

function getLengthOfLastWordUsingSubstring(s) {
    if (typeof s !== 'string') throw new TypeError('Input must be a string');
    
    s = s.trim();
    const lastSpaceIndex = s.lastIndexOf(' ');
    return s.substring(lastSpaceIndex + 1).length;
} 

const str1 = "hello aman";
getLengthOfLastWordUsingSubstring(str1);  //output: 4 

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