使用递归将字符串转换为整数
原文:https://www . geesforgeks . org/convert-a-string-to-a-整数-使用递归/
给定一个表示字符串的字符串 str ，任务是将给定的字符串转换成整数。 例:
输入: str = "1234" 输出: 1234 输入: str = "0145" 输出: 145
方法:写一个递归函数，取字符串的第一个数字，乘以适当的 10 次方，然后从第二个索引开始，将子字符串的递归结果相加。当传递的字符串由单个数字组成时，将出现终止条件。在这种情况下，返回由字符串表示的数字。 以下是上述办法的实施情况:
C++
// C++ implementation of the approach
#include<bits/stdc++.h>
using namespace std;
// Recursive function to convert
// string to integer
int stringToInt(string str)
{
// If the number represented as a string
// contains only a single digit
// then returns its value
if (str.length() == 1)
return (str[0] - '0');
// Recursive call for the sub-string
// starting at the second character
double y = stringToInt(str.substr(1));
// First digit of the number
double x = str[0] - '0';
// First digit multiplied by the
// appropriate power of 10 and then
// add the recursive result
// For example, xy = ((x * 10) + y)
x = x * pow(10, str.length() - 1) + y;
return int(x);
}
// Driver code
int main()
{
string str = "1235";
cout << (stringToInt(str)) << endl;
}
// This code is contributed by
// Surendra_Gangwar
Java 语言(一种计算机语言，尤用于创建网站)
// Java implementation of the approach
public class GFG {
// Recursive function to convert string to integer
static int stringToInt(String str)
{
// If the number represented as a string
// contains only a single digit
// then returns its value
if (str.length() == 1)
return (str.charAt(0) - '0');
// Recursive call for the sub-string
// starting at the second character
double y = stringToInt(str.substring(1));
// First digit of the number
double x = str.charAt(0) - '0';
// First digit multiplied by the
// appropriate power of 10 and then
// add the recursive result
// For example, xy = ((x * 10) + y)
x = x * Math.pow(10, str.length() - 1) + y;
return (int)(x);
}
// Driver code
public static void main(String[] args)
{
String str = "1235";
System.out.print(stringToInt(str));
}
}
Python 3
# Python3 implementation of the approach
# Recursive function to convert
# string to integer
def stringToInt(str):
# If the number represented as a string
# contains only a single digit
# then returns its value
if (len(str) == 1):
return ord(str[0]) - ord('0');
# Recursive call for the sub-string
# starting at the second character
y = stringToInt(str[1:]);
# First digit of the number
x = ord(str[0]) - ord('0');
# First digit multiplied by the
# appropriate power of 10 and then
# add the recursive result
# For example, xy = ((x * 10) + y)
x = x * (10**(len(str) - 1)) + y;
return int(x);
# Driver code
if __name__ == '__main__':
str = "1235";
print(stringToInt(str));
# This code is contributed by PrinciRaj1992
C
// C# implementation of the approach
using System;
class GFG
{
// Recursive function to convert string to integer
static int stringToInt(String str)
{
// If the number represented as a string
// contains only a single digit
// then returns its value
if (str.Length == 1)
return (str[0] - '0');
// Recursive call for the sub-string
// starting at the second character
double y = stringToInt(str.Substring(1));
// First digit of the number
double x = str[0] - '0';
// First digit multiplied by the
// appropriate power of 10 and then
// add the recursive result
// For example, xy = ((x * 10) + y)
x = x * Math.Pow(10, str.Length - 1) + y;
return (int)(x);
}
// Driver code
public static void Main(String[] args)
{
String str = "1235";
Console.Write(stringToInt(str));
}
}
// This code is contributed by Princi Singh
java 描述语言
<script>
// javascript implementation of the approach
// Recursive function to convert string to integer
function stringToInt(str)
{
// If the number represented as a string
// contains only a single digit
// then returns its value
if (str.length == 1)
return (str[0] - '0');
// Recursive call for the sub-string
// starting at the second character
var y = stringToInt(str.substring(1));
// First digit of the number
var x = str[0] - '0';
// First digit multiplied by the
// appropriate power of 10 and then
// add the recursive result
// For example, xy = ((x * 10) + y)
x = x * Math.pow(10, str.Length - 1) + y;
return (x);
}
// Driver code
var str = "1235".split()
document.write(stringToInt(str));
</script>
Output:
1235
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