Given numeric string str, the task is to remove all the leading zeros from a given string. If the string contains only zeros, then print a single “0”.
Examples:
Input: str = “0001234”
Output: 1234
Explanation:
Removal of leading substring “000” modifies the string to “1234”.
Hence, the final answer is “1234”.Input: str = “00000000”
Output: 0
Explanation:
There are no numbers except 0
Naive Approach:
The simplest approach to solve the problem is to traverse the string up to the first non-zero character present in the string and store the remaining string starting from that index as the answer. If the entire string is traversed, it means all the characters in the string are ‘0’. For this case, store “0” as the answer. Print the final answer.
Below is the implementation of the above idea:
C++
// C++ Program to remove all the leading// zeros from a given numeric string#include <bits/stdc++.h>using namespace std;// Function to remove the leading zerosstring removeLeadingZeros(string num){ // traverse the entire string for (int i = 0; i < num.length(); i++) { // check for the first non-zero character if (num[i] != '0') { // return the remaining string string res = num.substr(i); return res; } } // If the entire string is traversed // that means it didn't have a single // non-zero character, hence return "0" return "0";}// Driver Codeint main(){ string num = "1023"; cout << removeLeadingZeros(num) << endl; num = "00123"; cout << removeLeadingZeros(num) << endl;}// This code is contributed by phasing17 |
Java
// Java Program to remove all the leading //zeros from a given numeric stringimport java.io.*;class GFG{ // Function to remove the leading zeros static String removeLeadingZeros(String num) { //traverse the entire string for(int i=0;i<num.length();i++){ //check for the first non-zero character if(num.charAt(i)!='0'){ //return the remaining string String res = num.substring(i); return res; } } //If the entire string is traversed //that means it didn't have a single //non-zero character, hence return "0" return "0"; } // Driver Code public static void main(String[] args) { String num = "1023"; System.out.println(removeLeadingZeros(num)); num = "00123"; System.out.println(removeLeadingZeros(num)); }}// This code is contributed by shruti456rawal |
Python3
# Python Program to remove all the leading# zeros from a given numeric string# Function to remove the leading zerosdef removeLeadingZeros(num): # traverse the entire string for i in range(len(num)): # check for the first non-zero character if num[i] != '0': # return the remaining string res = num[i::]; return res; # If the entire string is traversed # that means it didn't have a single # non-zero character, hence return "0" return "0";# Driver Codenum = "1023";print(removeLeadingZeros(num));num = "00123";print(removeLeadingZeros(num));# This code is contributed by phasing17 |
C#
// C# Program to remove all the leading //zeros from a given numeric stringusing System;using System.Collections.Generic;class GFG{ // Function to remove the leading zeros static string removeLeadingZeros(string num) { // traverse the entire string for(int i = 0; i < num.Length; i++){ // check for the first non-zero character if(num[i] != '0') { // return the remaining string string res = num.Substring(i); return res; } } // If the entire string is traversed // that means it didn't have a single // non-zero character, hence return "0" return "0"; } // Driver Code public static void Main(string[] args) { string num = "1023"; Console.WriteLine(removeLeadingZeros(num)); num = "00123"; Console.WriteLine(removeLeadingZeros(num)); }}// This code is contributed by phasing17 |
Javascript
// JS Program to remove all the leading// zeros from a given numeric string// Function to remove the leading zerosfunction removeLeadingZeros(num){ // traverse the entire string for (var i = 0; i < num.length; i++) { // check for the first non-zero character if (num.charAt(i) != '0') { // return the remaining string let res = num.substr(i); return res; } } // If the entire string is traversed // that means it didn't have a single // non-zero character, hence return "0" return "0";}// Driver Codelet num = "1023";console.log(removeLeadingZeros(num));num = "00123";console.log(removeLeadingZeros(num));// This code is contributed by phasing17 |
Output
1023 123
Time Complexity: O(N)
Auxiliary Space: O(N)
Space-Efficient Approach:
Follow the steps below to solve the problem in constant space using Regular Expression:
- Create a Regular Expression as given below to remove the leading zeros
regex = “^0+(?!$)”
where:
^0+ match one or more zeros from the beginning of the string.
(?!$) is a negative look-ahead expression, where “$” means the end of the string.
- Use the inbuilt replaceAll() method of the String class which accepts two parameters, a Regular Expression, and a Replacement String.
- To remove the leading zeros, pass a Regex as the first parameter and empty string as the second parameter.
- This method replaces the matched value with the given string.
Below is the implementation of the above approach:
C++
// C++ Program to implement// the above approach#include <iostream>#include <regex>using namespace std;// Function to remove all leading// zeros from a given stringvoid removeLeadingZeros(string str){ // Regex to remove leading // zeros from a string const regex pattern("^0+(?!$)"); // Replaces the matched // value with given string str = regex_replace(str, pattern, ""); cout << str;}// Driver Codeint main(){ string str = "0001234"; removeLeadingZeros(str); return 0;} |
Java
// Java Program to implement// the above approachimport java.util.regex.*;class GFG { // Function to remove all leading // zeros from a given string public static void removeLeadingZeros(String str) { // Regex to remove leading // zeros from a string String regex = "^0+(?!$)"; // Replaces the matched // value with given string str = str.replaceAll(regex, ""); System.out.println(str); } // Driver Code public static void main(String args[]) { String str = "0001234"; removeLeadingZeros(str); }} |
Python3
# Python3 Program to implement # the above approach import re# Function to remove all leading # zeros from a given stringdef removeLeadingZeros(str): # Regex to remove leading # zeros from a string regex = "^0+(?!$)" # Replaces the matched # value with given string str = re.sub(regex, "", str) print(str)# Driver Code str = "0001234"removeLeadingZeros(str)# This code is contributed by avanitrachhadiya2155 |
C#
// C# program to implement// the above approachusing System;using System.Text.RegularExpressions;class GFG{// Function to remove all leading// zeros from a given stringpublic static void removeLeadingZeros(string str){ // Regex to remove leading // zeros from a string string regex = "^0+(?!$)"; // Replaces the matched // value with given string str = Regex.Replace(str, regex, ""); Console.WriteLine(str);}// Driver Codepublic static void Main(string[] args){ string str = "0001234"; removeLeadingZeros(str);}}// This code is contributed by ukasp |
Javascript
<script>// Javascript Program to implement// the above approach// Function to remove all leading // zeros from a given stringfunction removeLeadingZeros(str){ // Regex to remove leading // zeros from a string const regex = new RegExp("^0+(?!$)",'g'); // Replaces the matched // value with given string str = str.replaceAll(regex, ""); document.write(str);}// Driver Codelet str = "0001234"; removeLeadingZeros(str);// This code is contributed by unknown2108</script> |
Output
1234
Time Complexity: O(N), where N is the length of the string.
Auxiliary Space: O(1)
Java-specific approach: Refer to this article for the Java-specific approach using StringBuffer.
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