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Number of even substrings in a string of digits in C++
Given a string of digits, we need to find the count of even substrings in it. Let's see an example.
Input
num = "1234"
Output
6
The even substrings that can be formed from the given string are
2 12 4 34 234 1234
Algorithm
Initialise the string with digits.
Initialise the count to 0.
Iterate over the string.
Get the current digit by subtracting the char 0 from the current char digit.
Check whether the digit is even or not.
If the current digit is even, then add it's index plus 1 to the count.
- Return the count.
Implementation
Following is the implementation of the above algorithm in C++
#include<bits/stdc++.h>
using namespace std;
int getEvenSubstringsCount(char str[]) {
int len = strlen(str), count = 0;
for (int i = 0; i < len; i++) {
int currentDigit = str[i] - '0';
if (currentDigit % 2 == 0) {
count += i + 1;
}
}
return count;
}
int main() {
char str[] = "12345678";
cout << getEvenSubstringsCount(str) << endl;
return 0;
}Output
If you run the above code, then you will get the following result.
20
Updated on: 26-Oct-2021
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