# Convert A String To An Integer (without Using Built In Functions) ## Write a program to convert a string to an integer (without using built-in functions) ```txt Input : "123" Output : 123 ``` --- ```c #include /* printf, scanf */ /* assuming str includes only valid ascii numbers '0' - '9' */ int Atoi(char *str); int main() { /* test -- hardcoded and on stack */ char str[100] = {0}; scanf("%s",str); printf("%d\n",Atoi(str)); return 0; } int Atoi(char *str) { int ret = 0; while(*str != '\0') { ret *= 10; ret += *str - '0'; ++str; } return ret; } ``` ```cpp #include #include using namespace std; int ConvertAStringToAnInteger(string str) { int sign; if (str[0] == '-') { sign = -1; str = str.substr(1); } else { sign = 1; } int n = 0; for (int i = 0; i < str.size(); i++) { n += (str[i] - '0') * pow(10,str.size() - i -1); // char - '0' == (int) char } return n; } ``` ```csharp using System; class StringToInteger{ public static void convert(string s) { int num = 0; int n = s.Length; for(int i = 0; i < n; i++) num = num * 10 + ((int)s[i] - 48); Console.Write(num); } public static void Main(string[] args) { string s = "123"; convert(s); } } ``` ```java public class ConvertAStringToAnInteger { //Driven Code public static void main(String args[]) { // Given string of number String convertingString = "123456"; System.out.println("String Before Conversion : " + convertingString); int output = stringToint(convertingString); // Function Call System.out.println("int value as output " + output); // Print the answer } public static int stringToint(String str) { int i = 0, number = 0; // Initialize a variable boolean isNegative = false; int len = str.length(); if (str.charAt(0) == '-') { //checking string isNegative = true; i = 1; } while (i < len) { // Iterate till length of the string number *= 10; number += (str.charAt(i++) - '0'); } if (isNegative) number = -number; return number; } } ``` ```javascript function convertStringToInteger(str) { let [isNegative, result, num] = [false, str, 0]; if (result[0] === "-") { isNegative = true; result = result.slice(1); } for (let i = 0; i < result.length; i += 1) { const charCode = result.charCodeAt(i) - 48; const pow = 10 ** (result.length - i - 1); num += charCode * pow; } return isNegative ? num * -1 : num; } const str = "123"; console.log(`Input: ${str}, type: ${typeof str}`); console.log( `Output: ${convertStringToInteger( str, )}, type: ${typeof convertStringToInteger(str)}`, ); const strWithNegative = "-123"; console.log(`Input: ${strWithNegative}, type: ${typeof strWithNegative}`); console.log( `Output: ${convertStringToInteger( strWithNegative, )}, type: ${typeof convertStringToInteger(strWithNegative)}`, ); ``` ```kotlin fun main() { print("Input : ") println() var input = readLine() println("Convert string to Integer without using in built function : " + ConvertAStringToAnInteger(input!!)) } private fun ConvertAStringToAnInteger(num: String):Int { val number = Integer.valueOf(num) return number } ``` ```ruby def string_to_integer(str) result = 0 sign = 1 if str[0] == '-' sign = -1 str = str[1..-1] # Remove the negative sign from the string end str.each_char do |char| if char >= '0' && char <= '9' digit = char.ord - '0'.ord # Convert the character to an integer result = result * 10 + digit # Add the digit to the result else raise ArgumentError, "Invalid character: #{char}" end end return result * sign end # Input string print "Enter a string: " input_str = gets.chomp begin integer_result = string_to_integer(input_str) puts "Output: #{integer_result}" rescue ArgumentError => e puts "Error: #{e.message}" end ``` ```typescript /** * This function converts a string to an integer without using built-in functions with respect to the negative sign and the decimal point * @param {string} str - The string to be converted * @returns {number} - The converted integer * @example * convertStringToInteger("123") // returns 123 * convertStringToInteger("123.45") // returns 123 * * * @author [Ahmed Eltaher](https://github.com/ahmedheltaher) * */ function convertStringToInteger(str: string): number { let isNegative = false; if (str[0] === "-") { isNegative = true; str = str.slice(1); } if (str.indexOf(".") !== -1) { str = str.slice(0, str.indexOf(".")); } // Convert the string to an integer let num = 0; for (let i = 0; i < str.length; i++) { num += (str.charCodeAt(i) - 48) * Math.pow(10, str.length - i - 1); } // Handle negative numbers return num * (isNegative ? -1 : 1); } ``` ```go package main import ( "fmt" "math" "reflect" ) // Returns the passed number string as int. If the provided string isn't right it returns -1 func stringToInt(str string) int { var finalInt int = 0 for i := len(str) - 1; i >= 0; i-- { if str[i] >= 48 && str[i] <= 57 { power := float64(len(str) - i - 1) finalInt += int(str[i]-48) * int(math.Pow(10, power)) } else { return -1 } } return finalInt } func main() { result := stringToInt("230500") fmt.Println(result) fmt.Println(reflect.TypeOf(result)) } ``` ```php = '0' && $char <= '9') { // Multiply the result by 10 and add the digit $result = $result * 10 + (ord($char) - ord('0')); } else { // If the character is not a digit, break out of the loop break; } } // If the number is negative, convert the result to negative if ($isNegative) { $result = -$result; } return $result; } // Test cases $string = "2356234"; $integer = stringToInt($string); echo "String: $string\n"; echo "Integer: $integer\n"; ?> ``` ```python # -*- coding: utf-8 -*- """ Created on Sun Oct 9 16:08:39 2022 @author: smiti """ # Python3 program to convert a string to an integer (without using built-in functions) def convert(s: str) -> int: # function that will do the needful num = 0 # Initialize an integer variable # Iterate through all the characters of the string for i in s: # Subtract ascii value of 0 from the current digit num = num * 10 + (ord(i) - ord("0")) return num # return the ans # Take input: print(convert("123")) ```

Convert A String To An Integer (without Using Built In Functions)

Write a program to convert a string to an integer (without using built-in functions)

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