一串数字中偶数子串的数量
给定一串数字 0–9。任务是计算子串的数量，当转换为整数时，这些子串形成一个偶数。 例:
Input : str = "1234".
Output : 6
"2", "4", "12", "34", "234", "1234"
are 6 substring which are even.
Input : str = "154".
Output : 3
Input : str = "15".
Output : 0
对于偶数，子串必须以偶数结尾。我们找到字符串中所有的偶数数字，对于每个偶数数字，计算以它结尾的子字符串的数量。现在，观察子串的数量将是偶数加 1 的索引。
C++
// C++ program to count number of substring
// which are even integer in a string of digits.
#include<bits/stdc++.h>
using namespace std;
// Return the even number substrings.
int evenNumSubstring(char str[])
{
int len = strlen(str);
int count = 0;
for (int i = 0; i < len; i++)
{
int temp = str[i] - '0';
// If current digit is even, add
// count of substrings ending with
// it. The count is (i+1)
if (temp % 2 == 0)
count += (i + 1);
}
return count;
}
// Driven Program
int main()
{
char str[] = "1234";
cout << evenNumSubstring(str) << endl;
return 0;
}
Java 语言(一种计算机语言，尤用于创建网站)
// Java program to count number of
// substring which are even integer
// in a string of digits.
public class GFG {
// Return the even number substrings.
static int evenNumSubstring(String str)
{
int len = str.length();
int count = 0;
for (int i = 0; i < len; i++)
{
int temp = str.charAt(i) - '0';
// If current digit is even, add
// count of substrings ending with
// it. The count is (i+1)
if (temp % 2 == 0)
count += (i + 1);
}
return count;
}
public static void main(String args[])
{
String str= "1234";
System.out.println(evenNumSubstring(str));
}
}
// This code is contributed by Sam007.
Python 3
# Python 3 program to count number of substring
# which are even integer in a string of digits.
# Return the even number substrings.
def evenNumSubstring(str):
length = len(str)
count = 0
for i in range(0,length,1):
temp = ord(str[i]) - ord('0')
# If current digit is even, add
# count of substrings ending with
# it. The count is (i+1)
if (temp % 2 == 0):
count += (i + 1)
return count
# Driven Program
if __name__ == '__main__':
str = ['1','2','3','4']
print(evenNumSubstring(str))
# This code is contributed by
# Surendra_Gangwar
C
// C# program to count number of
// substring which are even integer
// in a string of digits.
using System;
public class GFG {
// Return the even number substrings.
static int evenNumSubstring(string str)
{
int len = str.Length;
int count = 0;
for (int i = 0; i < len; i++)
{
int temp = str[i] - '0';
// If current digit is even,
// add count of substrings
// ending with it. The count
// is (i+1)
if (temp % 2 == 0)
count += (i + 1);
}
return count;
}
// Driver code
public static void Main()
{
string str= "1234";
Console.Write(
evenNumSubstring(str));
}
}
// This code is contributed by Sam007.
服务器端编程语言（Professional Hypertext Preprocessor 的缩写）
<?php
// PHP program to count number
// of substring which are even
// integer in a string of digits.
// Return the even number substrings.
function evenNumSubstring($str)
{
$len = strlen($str);
$count = 0;
for ($i = 0; $i < $len; $i++)
{
$temp = $str[$i] - '0';
// If current digit is even, add
// count of substrings ending with
// it. The count is (i+1)
if ($temp % 2 == 0)
$count += ($i + 1);
}
return $count;
}
// Driver Code
$str = "1234";
echo evenNumSubstring($str),"\n" ;
// This code is contributed by jit_t
?>
java 描述语言
<script>
// Javascript program to count number of
// substring which are even integer
// in a string of digits.
// Return the even number substrings.
function evenNumSubstring(str)
{
let len = str.length;
let count = 0;
for (let i = 0; i < len; i++)
{
let temp = str[i] - '0';
// If current digit is even,
// add count of substrings
// ending with it. The count
// is (i+1)
if (temp % 2 == 0)
count += (i + 1);
}
return count;
}
let str= "1234";
document.write(evenNumSubstring(str));
</script>
输出:
6
时间复杂度: O(字符串长度)。
本文由 Anuj Chauhan 供稿。如果你喜欢 GeeksforGeeks 并想投稿，你也可以使用contribute.geeksforgeeks.org写一篇文章或者把你的文章邮寄到 contribute@geeksforgeeks.org。看到你的文章出现在极客博客主页上，帮助其他极客。 如果你发现任何不正确的地方，或者你想分享更多关于上面讨论的话题的信息，请写评论。
版权属于：月萌API www.moonapi.com，转载请注明出处
