struct Solution;
impl Solution {
fn number_of_subarrays(nums: Vec<i32>, k: i32) -> i32 {
let n = nums.len();
let mut count = vec![0; n + 1];
let k = k as usize;
count[0] = 1;
let mut prev = 0;
let mut res = 0;
for i in 0..n {
if nums[i] % 2 == 1 {
prev += 1;
}
count[prev] += 1;
if prev >= k {
res += count[prev - k];
}
}
res as i32
}
}
#[test]
fn test() {
let nums = vec![1, 1, 2, 1, 1];
let k = 3;
let res = 2;
assert_eq!(Solution::number_of_subarrays(nums, k), res);
let nums = vec![2, 4, 6];
let k = 1;
let res = 0;
assert_eq!(Solution::number_of_subarrays(nums, k), res);
let nums = vec![2, 2, 2, 1, 2, 2, 1, 2, 2, 2];
let k = 2;
let res = 16;
assert_eq!(Solution::number_of_subarrays(nums, k), res);
}