LeetCode 3247: Number of Subsequences with Odd Sum Solution
Master LeetCode problem 3247 (Number of Subsequences with Odd Sum), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.
3247. Number of Subsequences with Odd Sum
Problem Explanation
Explanation:
To solve this problem, we can use dynamic programming. We can iterate over the array and for each element, we can either include it in a subsequence or not include it. We can keep track of the count of subsequences ending at the current element with an even sum and the count of subsequences ending at the current element with an odd sum.
For each element, we can update the count of subsequences with even and odd sums based on the current element. At the end, we sum up all the subsequences with odd sums as our final result. :
Solution Code
class Solution {
public int numOfSubarrays(int[] nums) {
int mod = (int)1e9 + 7;
long even = 1, odd = 0, res = 0, sum = 0;
for (int num : nums) {
sum += num;
if (sum % 2 == 0) {
even++;
} else {
res = (res + even) % mod;
odd++;
}
}
return (int)res;
}
}Try It Yourself
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