Last updated on July 21st, 2024 at 04:29 am

Here, We see Remove K Digits LeetCode Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc. with different approaches.

List of all LeetCode Solution

Topics

Greedy, Stack

Companies

Google, Snapchat

Level of Question

Medium

Remove K Digits LeetCode Solution

Problem Statement

Given string num representing a non-negative integer num, and an integer k, return the smallest possible integer after removing k digits from num.

Example 1:
Input: num = “1432219”, k = 3
Output: “1219”
Explanation: Remove the three digits 4, 3, and 2 to form the new number 1219 which is the smallest.

Example 2:
Input: num = “10200”, k = 1
Output: “200”
Explanation: Remove the leading 1 and the number is 200. Note that the output must not contain leading zeroes.

Example 3:
Input: num = “10”, k = 2
Output: “0”
Explanation: Remove all the digits from the number and it is left with nothing which is 0.

1. Remove K Digits Leetcode Solution C++

class Solution {
public:
    string removeKdigits(string num, int k) {
        string ans="";
        for(char &c:num)
        {
            while(ans.size() && ans.back()>c &&k)
            {
                ans.pop_back();
                k--;
            }
            if(ans.size()||c!='0')ans.push_back(c);
        }
        while(ans.size()&&k--)
        {
            ans.pop_back();
        }
        return (ans=="")?"0":ans;
    }
};

2. Remove K Digits Leetcode Solution Java

class Solution {
    public String removeKdigits(String num, int k) {
        int len = num.length();
        if(k==len)        
            return "0";
        Stack<Character> stack = new Stack<>();
        int i =0;
        while(i<num.length()){
            while(k>0 && !stack.isEmpty() && stack.peek()>num.charAt(i)){
                stack.pop();
                k--;
            }
            stack.push(num.charAt(i));
            i++;
        }
        while(k>0){
            stack.pop();
            k--;            
        }
        StringBuilder sb = new StringBuilder();
        while(!stack.isEmpty())
            sb.append(stack.pop());
        sb.reverse();
        while(sb.length()>1 && sb.charAt(0)=='0')
            sb.deleteCharAt(0);
        return sb.toString();
    }
}

3. Remove K Digits Solution JavaScript

var removeKdigits = function(num, k) {
    const stack = [];
    let removed = 0;
    for(let n of num) {
        while(stack.length && n < stack[stack.length-1] && removed < k) {
            stack.pop();
            removed += 1;
        }
        stack.push(n);
    }
    while(removed < k) {
        stack.pop();
        removed += 1;
    }
    while(stack.length && stack[0] === '0') {
        stack.shift();
    }
    return stack.length ? stack.join('') : '0';
};

4. Remove K Digits Solution Python

class Solution(object):
    def removeKdigits(self, num, k):
        stack = []
        for n in num:
            while( stack and int(stack[-1]) > int(n) and k):
                stack.pop()
                k -= 1
            stack.append(str(n))
        while(k):
            stack.pop()
            k -= 1
        i = 0
        while( i <len(stack) and stack[i] == "0" ):
            i += 1
        return ''.join(stack[i:]) if (len(stack[i:]) > 0) else "0"