Datasets:
Tasks:
Text Generation
Modalities:
Text
Formats:
json
Languages:
English
Size:
< 1K
ArXiv:
Tags:
competitive-programming
code-generation
specification-generation
proof-generation
verification
rust
License:
| use vstd::prelude::*; | |
| fn main() {} | |
| verus! { | |
| pub struct Solution; | |
| pub open spec fn subarray_sum(s: Seq<i32>, i: int, j: int) -> int | |
| decreases j - i + 1, | |
| { | |
| if i > j { 0 } | |
| else { subarray_sum(s, i, j - 1) + s[j] as int } | |
| } | |
| pub open spec fn count_odd_ending(s: Seq<i32>, end_idx: int, k: int) -> int | |
| decreases k + 1, | |
| { | |
| if k < 0 { 0 } | |
| else { | |
| count_odd_ending(s, end_idx, k - 1) | |
| + if subarray_sum(s, k, end_idx) % 2 != 0 { 1 as int } else { 0 as int } | |
| } | |
| } | |
| pub open spec fn count_odd_subarrays(s: Seq<i32>, n: int) -> int | |
| decreases n, | |
| { | |
| if n <= 0 { 0 } | |
| else { | |
| count_odd_subarrays(s, n - 1) + count_odd_ending(s, n - 1, n - 1) | |
| } | |
| } | |
| impl Solution { | |
| pub fn num_of_subarrays(arr: Vec<i32>) -> (res: i32) | |
| requires | |
| 1 <= arr.len() <= 100_000, | |
| forall |i: int| 0 <= i < arr.len() ==> 1 <= arr[i] <= 100, | |
| ensures | |
| 0 <= res < 1_000_000_007, | |
| res as int == count_odd_subarrays(arr@, arr.len() as int) % 1_000_000_007, | |
| { | |
| let mut odd: i64 = 0; | |
| let mut even: i64 = 0; | |
| let mut res: i64 = 0; | |
| let mut i: usize = 0; | |
| while i < arr.len() { | |
| if arr[i] % 2 == 0 { | |
| even = even + 1; | |
| } else { | |
| let tmp = odd; | |
| odd = even + 1; | |
| even = tmp; | |
| } | |
| res = (res + odd) % 1_000_000_007i64; | |
| i = i + 1; | |
| } | |
| res as i32 | |
| } | |
| } | |
| } | |