从任意基数转换为十进制，反之亦然
原文:https://www . geesforgeks . org/convert-base-decimal-反之亦然/
给定一个数字及其基数，将其转换为十进制。数字的基数可以是任何可以用 0 到 9 和 A 到 z 表示所有数字的东西。A 的值是 10，B 的值是 11，以此类推。写一个函数把数字转换成十进制。
示例:
Input number is given as string and output is an integer.
Input: str = "1100", base = 2
Output: 12
Input: str = "11A", base = 16
Output: 282
Input: str = "123", base = 8
Output: 83
我们强烈建议你尽量减少浏览器，先自己试试这个。 我们总是可以用下面的公式从任意基数转换成十进制。
"str" is input number as a string
"base" is the base of the input number.
Decimal Equivalent is,
1*str[len-1] + base*str[len-2] + (base)2*str[len-3] + ...
下面是上述公式的实现。
C
// C program to convert a number from any base
// to decimal
#include <stdio.h>
#include <string.h>
// To return value of a char. For example, 2 is
// returned for '2'. 10 is returned for 'A', 11
// for 'B'
int val(char c)
{
if (c >= '0' && c <= '9')
return (int)c - '0';
else
return (int)c - 'A' + 10;
}
// Function to convert a number from given base 'b'
// to decimal
int toDeci(char *str, int base)
{
int len = strlen(str);
int power = 1; // Initialize power of base
int num = 0; // Initialize result
int i;
// Decimal equivalent is str[len-1]*1 +
// str[len-2]*base + str[len-3]*(base^2) + ...
for (i = len - 1; i >= 0; i--)
{
// A digit in input number must be
// less than number's base
if (val(str[i]) >= base)
{
printf("Invalid Number");
return -1;
}
num += val(str[i]) * power;
power = power * base;
}
return num;
}
// Driver code
int main()
{
char str[] = "11A";
int base = 16;
printf("Decimal equivalent of %s in base %d is "
" %d\n", str, base, toDeci(str, base));
return 0;
}
Java 语言(一种计算机语言，尤用于创建网站)
// Java program to convert
// a number from any base
// to decimal
import java.io.*;
class GFG
{
// To return value of a char.
// For example, 2 is returned
// for '2'. 10 is returned
// for 'A', 11 for 'B'
static int val(char c)
{
if (c >= '0' && c <= '9')
return (int)c - '0';
else
return (int)c - 'A' + 10;
}
// Function to convert a
// number from given base
// 'b' to decimal
static int toDeci(String str,
int base)
{
int len = str.length();
int power = 1; // Initialize
// power of base
int num = 0; // Initialize result
int i;
// Decimal equivalent is
// str[len-1]*1 + str[len-2] *
// base + str[len-3]*(base^2) + ...
for (i = len - 1; i >= 0; i--)
{
// A digit in input number
// must be less than
// number's base
if (val(str.charAt(i)) >= base)
{
System.out.println("Invalid Number");
return -1;
}
num += val(str.charAt(i)) * power;
power = power * base;
}
return num;
}
// Driver code
public static void main (String[] args)
{
String str = "11A";
int base = 16;
System.out.println("Decimal equivalent of "+
str + " in base "+ base +
" is "+ " "+
toDeci(str, base));
}
}
// This code is contributed
// by anuj_67.
Python 3
# Python program to convert a
# number from any base to decimal
# To return value of a char.
# For example, 2 is returned
# for '2'. 10 is returned for 'A',
# 11 for 'B'
def val(c):
if c >= '0' and c <= '9':
return ord(c) - ord('0')
else:
return ord(c) - ord('A') + 10;
# Function to convert a number
# from given base 'b' to decimal
def toDeci(str,base):
llen = len(str)
power = 1 #Initialize power of base
num = 0 #Initialize result
# Decimal equivalent is str[len-1]*1 +
# str[len-2]*base + str[len-3]*(base^2) + ...
for i in range(llen - 1, -1, -1):
# A digit in input number must
# be less than number's base
if val(str[i]) >= base:
print('Invalid Number')
return -1
num += val(str[i]) * power
power = power * base
return num
# Driver code
strr = "11A"
base = 16
print('Decimal equivalent of', strr,
'in base', base, 'is',
toDeci(strr, base))
# This code is contributed
# by Sahil shelangia
C
// C# program to convert
// a number from any base
// to decimal
using System;
class GFG
{
// To return value of a char.
// For example, 2 is returned
// for '2'. 10 is returned
// for 'A', 11 for 'B'
static int val(char c)
{
if (c >= '0' && c <= '9')
return (int)c - '0';
else
return (int)c - 'A' + 10;
}
// Function to convert a
// number from given base
// 'b' to decimal
static int toDeci(string str,
int b_ase)
{
int len = str.Length;
int power = 1; // Initialize
// power of base
int num = 0; // Initialize result
int i;
// Decimal equivalent is
// str[len-1]*1 + str[len-2] *
// base + str[len-3]*(base^2) + ...
for (i = len - 1; i >= 0; i--)
{
// A digit in input number
// must be less than
// number's base
if (val(str[i]) >= b_ase)
{
Console.WriteLine("Invalid Number");
return -1;
}
num += val(str[i]) * power;
power = power * b_ase;
}
return num;
}
// Driver code
public static void Main ()
{
string str = "11A";
int b_ase = 16;
Console.WriteLine("Decimal equivalent of "+
str + " in base "+ b_ase +
" is " + toDeci(str, b_ase));
}
}
// This code is contributed
// by anuj_67.
服务器端编程语言（Professional Hypertext Preprocessor 的缩写）
<?php
// PHP program to convert a number from
// any base to decimal
// To return value of a char. For example,
// 2 is returned for '2'. 10 is returned
// for 'A', 11 for 'B'
function val($c)
{
if ($c >= '0' && $c <= '9')
return ord($c) - ord('0');
else
return ord($c) - ord('A') + 10;
}
// Function to convert a number from given
// base 'b' to decimal
function toDeci($str, $base)
{
$len = strlen($str);
$power = 1; // Initialize power of base
$num = 0; // Initialize result
// Decimal equivalent is str[len-1]*1 +
// str[len-2]*base + str[len-3]*(base^2) + ...
for ($i = $len - 1; $i >= 0; $i--)
{
// A digit in input number must be
// less than number's base
if (val($str[$i]) >= $base)
{
print("Invalid Number");
return -1;
}
$num += val($str[$i]) * $power;
$power = $power * $base;
}
return $num;
}
// Driver code
$str = "11A";
$base = 16;
print("Decimal equivalent of $str " .
"in base $base is " . toDeci($str, $base));
// This code is contributed by mits
?>
java 描述语言
<script>
// Javascript program to convert
// a number from any base
// to decimal
// To return value of a char.
// For example, 2 is returned
// for '2'. 10 is returned
// for 'A', 11 for 'B'
function val(c)
{
if (c >= '0'.charCodeAt() &&
c <= '9'.charCodeAt())
return (c - '0'.charCodeAt());
else
return (c - 'A'.charCodeAt() + 10);
}
// Function to convert a
// number from given base
// 'b' to decimal
function toDeci(str, b_ase)
{
let len = str.length;
// Initialize
// power of base
let power = 1;
// Initialize result
let num = 0;
let i;
// Decimal equivalent is
// str[len-1]*1 + str[len-2] *
// base + str[len-3]*(base^2) + ...
for(i = len - 1; i >= 0; i--)
{
// A digit in input number
// must be less than
// number's base
if (val(str[i].charCodeAt()) >= b_ase)
{
document.write("Invalid Number");
return -1;
}
num += val(str[i].charCodeAt()) * power;
power = power * b_ase;
}
return num;
}
// Driver code
let str = "11A";
let b_ase = 16;
document.write("Decimal equivalent of "+
str + " in base "+ b_ase +
" is " + toDeci(str, b_ase));
// This code is contributed by divyesh072019
</script>
输出:
Decimal equivalent of 11A in base 16 is 282
怎么做反转？ 让给定的输入十进制数为“输入数”，目标基数为“基数”。我们反复用基数除 inputNum，并存储余数。我们最终反转得到的字符串。下面是 C 实现。
C
// C Program to convert decimal to any given base
#include <stdio.h>
#include <string.h>
// To return char for a value. For example '2'
// is returned for 2\. 'A' is returned for 10\. 'B'
// for 11
char reVal(int num)
{
if (num >= 0 && num <= 9)
return (char)(num + '0');
else
return (char)(num - 10 + 'A');
}
// Utility function to reverse a string
void strev(char *str)
{
int len = strlen(str);
int i;
for (i = 0; i < len/2; i++)
{
char temp = str[i];
str[i] = str[len-i-1];
str[len-i-1] = temp;
}
}
// Function to convert a given decimal number
// to a base 'base' and
char* fromDeci(char res[], int base, int inputNum)
{
int index = 0; // Initialize index of result
// Convert input number is given base by repeatedly
// dividing it by base and taking remainder
while (inputNum > 0)
{
res[index++] = reVal(inputNum % base);
inputNum /= base;
}
res[index] = '\0';
// Reverse the result
strev(res);
return res;
}
// Driver program
int main()
{
int inputNum = 282, base = 16;
char res[100];
printf("Equivalent of %d in base %d is "
" %s\n", inputNum, base, fromDeci(res, base, inputNum));
return 0;
}
Java 语言(一种计算机语言，尤用于创建网站)
// Java Program to convert decimal to any given base
import java.lang.*;
import java.io.*;
import java.util.*;
class GFG
{
// To return char for a value. For
// example '2' is returned for 2.
// 'A' is returned for 10\. 'B' for 11
static char reVal(int num)
{
if (num >= 0 && num <= 9)
return (char)(num + 48);
else
return (char)(num - 10 + 65);
}
// Function to convert a given decimal number
// to a base 'base' and
static String fromDeci(int base1, int inputNum)
{
String s = "";
// Convert input number is given
// base by repeatedly dividing it
// by base and taking remainder
while (inputNum > 0)
{
s += reVal(inputNum % base1);
inputNum /= base1;
}
StringBuilder ix = new StringBuilder();
// append a string into StringBuilder input1
ix.append(s);
// Reverse the result
return new String(ix.reverse());
}
// Driver code
public static void main (String[] args)
{
int inputNum = 282, base1 = 16;
System.out.println("Equivalent of " + inputNum +
" in base "+base1+" is " +
fromDeci(base1, inputNum));
}
}
// This code is contributed by mits
Python 3
# Python3 Program to convert decimal to
# any given base
# To return char for a value. For example
# '2' is returned for 2\. 'A' is returned
# for 10\. 'B' for 11
def reVal(num):
if (num >= 0 and num <= 9):
return chr(num + ord('0'));
else:
return chr(num - 10 + ord('A'));
# Utility function to reverse a string
def strev(str):
len = len(str);
for i in range(int(len / 2)):
temp = str[i];
str[i] = str[len - i - 1];
str[len - i - 1] = temp;
# Function to convert a given decimal
# number to a base 'base' and
def fromDeci(res, base, inputNum):
index = 0; # Initialize index of result
# Convert input number is given base
# by repeatedly dividing it by base
# and taking remainder
while (inputNum > 0):
res+= reVal(inputNum % base);
inputNum = int(inputNum / base);
# Reverse the result
res = res[::-1];
return res;
# Driver Code
inputNum = 282;
base = 16;
res = "";
print("Equivalent of", inputNum, "in base",
base, "is", fromDeci(res, base, inputNum));
# This code is contributed by mits
C
// C# Program to convert decimal to any given base
using System;
using System.Collections;
class GFG
{
// To return char for a value. For
// example '2' is returned for 2.
// 'A' is returned for 10\. 'B' for 11
static char reVal(int num)
{
if (num >= 0 && num <= 9)
return (char)(num + 48);
else
return (char)(num - 10 + 65);
}
// Function to convert a given decimal number
// to a base 'base' and
static string fromDeci(int base1, int inputNum)
{
string s = "";
// Convert input number is given
// base by repeatedly dividing it
// by base and taking remainder
while (inputNum > 0)
{
s += reVal(inputNum % base1);
inputNum /= base1;
}
char[] res = s.ToCharArray();
// Reverse the result
Array.Reverse(res);
return new String(res);
}
// Driver code
static void Main()
{
int inputNum = 282, base1 = 16;
Console.WriteLine("Equivalent of " + inputNum +
" in base "+base1+" is " +
fromDeci(base1, inputNum));
}
}
// This code is contributed by mits
服务器端编程语言（Professional Hypertext Preprocessor 的缩写）
<?php
// PHP Program to convert decimal to
// any given base
// To return char for a value. For example '2'
// is returned for 2\. 'A' is returned for 10.
// 'B' for 11
function reVal($num)
{
if ($num >= 0 && $num <= 9)
return chr($num + ord('0'));
else
return chr($num - 10 + ord('A'));
}
// Utility function to reverse a string
function strev($str)
{
$len = strlen($str);
for ($i = 0; $i < $len / 2; $i++)
{
$temp = $str[$i];
$str[$i] = $str[$len - $i - 1];
$str[$len - $i - 1] = $temp;
}
}
// Function to convert a given decimal
// number to a base 'base' and
function fromDeci($res, $base, $inputNum)
{
$index = 0; // Initialize index of result
// Convert input number is given base
// by repeatedly dividing it by base
// and taking remainder
while ($inputNum > 0)
{
$res.= reVal($inputNum % $base);
$inputNum = (int)($inputNum / $base);
}
// Reverse the result
$res = strrev($res);
return $res;
}
// Driver Code
$inputNum = 282;
$base = 16;
$res = "";
print("Equivalent of $inputNum in base $base is " .
fromDeci($res, $base, $inputNum));
// This code is contributed by mits
?>
java 描述语言
<script>
// Javascript Program to convert decimal to any given base
// To return char for a value. For
// example '2' is returned for 2.
// 'A' is returned for 10\. 'B' for 11
function reVal(num)
{
if (num >= 0 && num <= 9)
return String.fromCharCode(num + 48);
else
return String.fromCharCode(num - 10 + 65);
}
// Function to convert a given decimal number
// to a base 'base' and
function fromDeci(base1, inputNum)
{
let s = "";
// Convert input number is given
// base by repeatedly dividing it
// by base and taking remainder
while (inputNum > 0)
{
s += reVal(inputNum % base1);
inputNum = parseInt(inputNum / base1, 10);
}
let res = s.split('');
// Reverse the result
res.reverse();
return res.join("");
}
let inputNum = 282, base1 = 16;
document.write("Equivalent of " + inputNum +
" in base "+base1+" is " +
fromDeci(base1, inputNum));
// This code is contributed by rameshtravel07.
</script>
输出:
Equivalent of 282 in base 16 is 11A
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