检查一个大数是否能被 9 整除
给定一个数,任务是找出这个数是否能被 9 整除。输入的数字可能很大,即使我们使用 long long int 也可能无法存储。
示例:
Input : n = 69354
Output : Yes
Input : n = 234567876799333
Output : No
Input : n = 3635883959606670431112222
Output : No
因为输入的数字可能非常大,所以我们不能用 n % 9 来检查一个数字是否能被 9 整除,尤其是在像 C/C++这样的语言中。这个想法基于以下事实。
A number is divisible by 9 if sum of its digits is divisible by 9.
插图:
For example n = 9432
Sum of digits = 9 + 4 + 3 + 2
= 18
Since sum is divisible by 9,
answer is Yes.
这是如何工作的?
Let us consider 1332, we can write it as
1332 = 1*1000 + 3*100 + 3*10 + 2
The proof is based on below observation:
Remainder of 10i divided by 9 is 1
So powers of 10 only results in remainder 1
when divided by 9.
Remainder of "1*1000 + 3*100 + 3*10 + 2"
divided by 9 can be written as :
1*1 + 3*1 + 3*1 + 2 = 9
The above expression is basically sum of
all digits.
Since 9 is divisible by 9, answer is yes.
以下是上述想法的实现。
C++
// C++ program to find if a number is divisible by
// 9 or not
#include<bits/stdc++.h>
using namespace std;
// Function to find that number divisible by 9 or not
int check(string str)
{
// Compute sum of digits
int n = str.length();
int digitSum = 0;
for (int i=0; i<n; i++)
digitSum += (str[i]-'0');
// Check if sum of digits is divisible by 9.
return (digitSum % 9 == 0);
}
// Driver code
int main()
{
string str = "99333";
check(str)? cout << "Yes" : cout << "No ";
return 0;
}
Java 语言(一种计算机语言,尤用于创建网站)
// Java program to find if a number is
// divisible by 9 or not
class IsDivisible
{
// Function to find that number
// is divisible by 9 or not
static boolean check(String str)
{
// Compute sum of digits
int n = str.length();
int digitSum = 0;
for (int i=0; i<n; i++)
digitSum += (str.charAt(i)-'0');
// Check if sum of digits is divisible by 9.
return (digitSum % 9 == 0);
}
// main function
public static void main (String[] args)
{
String str = "99333";
if(check(str))
System.out.println("Yes");
else
System.out.println("No");
}
}
Python 3
# Python 3 program to
# find if a number is
# divisible by
# 9 or not
# Function to find that
# number divisible by 9
# or not
def check(st) :
# Compute sum of digits
n = len(st)
digitSum = 0
for i in range(0,n) :
digitSum = digitSum + (int)(st[i])
# Check if sum of digits
# is divisible by 9.
return (digitSum % 9 == 0)
# Driver code
st = "99333"
if(check(st)) :
print("Yes")
else :
print("No")
# This code is contributed by Nikita Tiwari.
C
// C# program to find if a number is
// divisible by 9 or not.
using System;
class GFG {
// Function to find that number
// is divisible by 9 or not
static bool check(String str)
{
// Compute sum of digits
int n = str.Length;
int digitSum = 0;
for (int i = 0; i < n; i++)
digitSum += (str[i] - '0');
// Check if sum of digits is
// divisible by 9.
return (digitSum % 9 == 0);
}
// main function
public static void Main ()
{
String str = "99333";
if(check(str))
Console.Write("Yes");
else
Console.Write("No");
}
}
// This code is Contributed by
// nitin mittal.
服务器端编程语言(Professional Hypertext Preprocessor 的缩写)
<?php
// PHP program to find if a number
// is divisible by 9 or not
// Function to find that
// number divisible by 9 or not
function check($str)
{
// Compute sum of digits
$n = strlen($str);
$digitSum = 0;
for ($i = 0; $i < $n; $i++)
$digitSum += ($str[$i] - '0');
// Check if sum of digits
// is divisible by 9.
return ($digitSum % 9 == 0);
}
// Driver code
$str = "99333";
$x = check($str) ? "Yes" : "No ";
echo($x);
// This code is contributed by Ajit.
?>
java 描述语言
<script>
// Javascript program to find if a number
// is divisible by 9 or not
// Function to find that
// number divisible by 9 or not
function check(str)
{
// Compute sum of digits
let n = str.length;
let digitSum = 0;
for(let i = 0; i < n; i++)
digitSum += (str[i] - '0');
// Check if sum of digits
// is divisible by 9.
return (digitSum % 9 == 0);
}
// Driver code
let str = "99333";
let x = check(str) ? "Yes" : "No ";
document.write(x);
// This code is contributed by _saurabh_jaiswal.
</script>
输出:
Yes
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