Truncate Sentence LeetCode Solution - The Coding Shala

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 In this post, we will learn how to solve LeetCode's Truncate Sentence problem and will implement its solution in Java.

Truncate Sentence Problem

You are given a sentence s​​​​​​ and an integer k​​​​​​. You want to truncate s​​​​​​ such that it contains only the first k​​​​​​ words. Return s​​​​​​ after truncating it.

Example 1:
Input: s = "Hello how are you Contestant", k = 4
Output: "Hello how are you"
Explanation:
The words in s are ["Hello", "how" "are", "you", "Contestant"].
The first 4 words are ["Hello", "how", "are", "you"].
Hence, you should return "Hello how are you".

Example 2:
Input: s = "chopper is not a tanuki", k = 5
Output: "chopper is not a tanuki"

Practice this problem on LeetCode.

LeetCode - Truncate Sentence Java Solution

Approach 1

First, convert the given string to an array then take the first k words and make a string and return.

Java Program: 

class Solution {
    public String truncateSentence(String s, int k) {
        // change string to array
        String[] arr = s.split(" ");
        StringBuilder sb = new StringBuilder();
        
        //make string using k words
        for(int i = 0; i < k; i++) {
            sb.append(arr[i]+ " ");
        }
        
        //trim is used to remove last white space
        return sb.toString().trim();
    }
}

Approach 2

Using Java's in-built methods.

Java Program: 

class Solution {
    public String truncateSentence(String s, int k) {
        return String.join(" " , Arrays.copyOfRange(s.split(" "), 0, k));
    }
}

Approach 3

Not using split. We can count white space and return string according to that. This program is performed better than the two above.

Java Program: 

class Solution {
    public String truncateSentence(String s, int k) {
        int spaceCount = 0;
        int index = 0;
        while(index < s.length()) {
            if(s.charAt(index) == ' ') spaceCount++;
            if(spaceCount == k) break;
            index++;
        }
        return s.substring(0, index);
    }
}


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