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:
File size: 3,163 Bytes
e5529fb | 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 | use vstd::prelude::*;
fn main() {}
verus! {
pub struct Solution;
pub open spec fn abs_diff(a: int, b: int) -> int {
if a >= b { a - b } else { b - a }
}
pub open spec fn spec_max(a: int, b: int) -> int {
if a >= b { a } else { b }
}
pub open spec fn spec_min(a: int, b: int) -> int {
if a <= b { a } else { b }
}
pub open spec fn array_value_upto(s: Seq<i32>, n: int) -> int
decreases n
{
if n <= 0 { 0 }
else { array_value_upto(s, n - 1) + abs_diff(s[n - 1] as int, s[n] as int) }
}
pub open spec fn array_value(s: Seq<i32>) -> int {
array_value_upto(s, s.len() as int - 1)
}
pub open spec fn reversal_gain(s: Seq<i32>, l: int, r: int) -> int {
let n = s.len() as int;
let left_change = if l > 0 {
abs_diff(s[l - 1] as int, s[r] as int) - abs_diff(s[l - 1] as int, s[l] as int)
} else { 0int };
let right_change = if r < n - 1 {
abs_diff(s[l] as int, s[r + 1] as int) - abs_diff(s[r] as int, s[r + 1] as int)
} else { 0int };
left_change + right_change
}
impl Solution {
pub fn max_value_after_reverse(nums: Vec<i32>) -> (result: i32)
requires
2 <= nums@.len() <= 30000,
forall |i: int| 0 <= i < nums@.len() ==> -100000 <= #[trigger] nums@[i] <= 100000,
forall |l: int, r: int| 0 <= l && l <= r && r < nums@.len() ==>
array_value(nums@) + #[trigger] reversal_gain(nums@, l, r) <= i32::MAX as int,
ensures
forall |l: int, r: int| 0 <= l && l <= r && r < nums@.len() ==>
result as int >= array_value(nums@) + #[trigger] reversal_gain(nums@, l, r),
exists |l: int, r: int| 0 <= l && l <= r && r < nums@.len() &&
result as int == array_value(nums@) + reversal_gain(nums@, l, r),
{
let n = nums.len();
let mut total: i64 = 0;
let mut gain: i64 = 0;
let mut min_of_max: i64 = 200001;
let mut max_of_min: i64 = -200001;
let mut i: usize = 0;
while i < n - 1 {
let a = nums[i] as i64;
let b = nums[i + 1] as i64;
let diff: i64 = if a >= b { a - b } else { b - a };
total = total + diff;
let first = nums[0] as i64;
let last = nums[n - 1] as i64;
let g1: i64 = (if first >= b { first - b } else { b - first }) - diff;
let g2: i64 = (if last >= a { last - a } else { a - last }) - diff;
if g1 > gain {
gain = g1;
}
if g2 > gain {
gain = g2;
}
let pair_max: i64 = if a >= b { a } else { b };
let pair_min: i64 = if a <= b { a } else { b };
if pair_max < min_of_max {
min_of_max = pair_max;
}
if pair_min > max_of_min {
max_of_min = pair_min;
}
i = i + 1;
}
let interior: i64 = if max_of_min > min_of_max {
2 * (max_of_min - min_of_max)
} else {
0
};
if interior > gain {
gain = interior;
}
(total + gain) as i32
}
}
}
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