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Text Generation
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Formats:
json
Languages:
English
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< 1K
ArXiv:
Tags:
competitive-programming
code-generation
specification-generation
proof-generation
verification
rust
License:
File size: 2,619 Bytes
033007a | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 | use vstd::prelude::*;
fn main() {}
verus! {
pub struct Solution;
pub open spec fn sum_even(s: Seq<i32>, start: int, end: int) -> int
decreases end - start,
{
if start >= end {
0
} else if start % 2 == 0 {
s[start] as int + sum_even(s, start + 1, end)
} else {
sum_even(s, start + 1, end)
}
}
pub open spec fn sum_odd(s: Seq<i32>, start: int, end: int) -> int
decreases end - start,
{
if start >= end {
0
} else if start % 2 == 1 {
s[start] as int + sum_odd(s, start + 1, end)
} else {
sum_odd(s, start + 1, end)
}
}
pub open spec fn even_sum_after_removal(s: Seq<i32>, i: int) -> int {
sum_even(s, 0, i) + sum_odd(s, i + 1, s.len() as int)
}
pub open spec fn odd_sum_after_removal(s: Seq<i32>, i: int) -> int {
sum_odd(s, 0, i) + sum_even(s, i + 1, s.len() as int)
}
pub open spec fn is_fair_after_removal(s: Seq<i32>, i: int) -> bool {
even_sum_after_removal(s, i) == odd_sum_after_removal(s, i)
}
pub open spec fn count_fair(s: Seq<i32>, start: int, end: int) -> int
decreases end - start,
{
if start >= end {
0
} else if is_fair_after_removal(s, start) {
1 + count_fair(s, start + 1, end)
} else {
count_fair(s, start + 1, end)
}
}
impl Solution {
pub fn ways_to_make_fair(nums: Vec<i32>) -> (res: i32)
requires
1 <= nums.len() <= 100_000,
forall |i: int| 0 <= i < nums.len() ==> 1 <= #[trigger] nums[i] <= 10_000,
ensures
res == count_fair(nums@, 0, nums@.len() as int),
{
let n = nums.len();
let mut right_even: i64 = 0;
let mut right_odd: i64 = 0;
let mut i: usize = 0;
while i < n {
if i % 2 == 0 {
right_even = right_even + nums[i] as i64;
} else {
right_odd = right_odd + nums[i] as i64;
}
i = i + 1;
}
let mut left_even: i64 = 0;
let mut left_odd: i64 = 0;
let mut result: i32 = 0;
i = 0;
while i < n {
if i % 2 == 0 {
right_even = right_even - nums[i] as i64;
} else {
right_odd = right_odd - nums[i] as i64;
}
if left_even + right_odd == left_odd + right_even {
result = result + 1;
}
if i % 2 == 0 {
left_even = left_even + nums[i] as i64;
} else {
left_odd = left_odd + nums[i] as i64;
}
i = i + 1;
}
result
}
}
}
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