VeriContest_Lite / leetcode /lc1671 /code_spec.rs
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use vstd::prelude::*;
fn main() {}
verus! {
pub struct Solution;
impl Solution {
pub open spec fn is_mountain_subseq(nums: Seq<i32>, indices: Seq<int>, peak: int) -> bool {
&&& indices.len() >= 3
&&& 0 < peak < indices.len() - 1
&&& (forall |k: int| 0 <= k < indices.len() ==> 0 <= (#[trigger] indices[k]) < nums.len())
&&& (forall |k: int| 0 <= k < peak ==>
indices[k] < indices[k + 1] && (#[trigger] nums[indices[k]]) < nums[indices[k + 1]])
&&& (forall |k: int| peak <= k < indices.len() - 1 ==>
indices[k] < indices[k + 1] && (#[trigger] nums[indices[k]]) > nums[indices[k + 1]])
}
pub fn minimum_mountain_removals(nums: Vec<i32>) -> (result: i32)
requires
3 <= nums.len() <= 1000,
forall |i: int| 0 <= i < nums.len() ==> 1 <= #[trigger] nums[i] <= 1_000_000_000i32,
exists |a: int, b: int, c: int| 0 <= a < b < c < nums.len() as int
&& nums[a] < nums[b] && nums[b] > nums[c],
ensures
result >= 0,
exists |indices: Seq<int>, peak: int| Self::is_mountain_subseq(nums@, indices, peak)
&& indices.len() == nums.len() - result as int,
forall |indices: Seq<int>, peak: int| Self::is_mountain_subseq(nums@, indices, peak)
==> indices.len() <= nums.len() - result as int,
{
let n = nums.len();
let mut lis: Vec<i32> = Vec::new();
let mut idx: usize = 0;
while idx < n {
lis.push(1i32);
idx = idx + 1;
}
let mut i: usize = 1;
while i < n {
let mut j: usize = 0;
while j < i {
if nums[j] < nums[i] {
if lis[j] + 1 > lis[i] {
lis.set(i, lis[j] + 1);
}
}
j = j + 1;
}
i = i + 1;
}
let mut lds: Vec<i32> = Vec::new();
idx = 0;
while idx < n {
lds.push(1i32);
idx = idx + 1;
}
let mut k: usize = 1;
while k < n {
let i_idx: usize = n - 1 - k;
let mut j: usize = i_idx + 1;
while j < n {
if nums[j] < nums[i_idx] {
if lds[j] + 1 > lds[i_idx] {
lds.set(i_idx, lds[j] + 1);
}
}
j = j + 1;
}
k = k + 1;
}
let mut result: i32 = n as i32;
let mut i2: usize = 0;
while i2 < n {
if lis[i2] > 1 && lds[i2] > 1 {
let mountain_len: i32 = lis[i2] + lds[i2] - 1;
let removals: i32 = n as i32 - mountain_len;
if removals < result {
result = removals;
}
}
i2 = i2 + 1;
}
result
}
}
}