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use std::{
cmp::PartialEq,
iter::Sum,
ops::{Add, Sub},
};
pub fn brutal<T>(arr: &[T]) -> Option<usize>
where
T: for<'a> Sum<&'a T>
+ for<'a> Sub<&'a T, Output = T>
+ for<'a> Add<&'a T, Output = T>
+ PartialEq
+ Copy,
{
let sum: T = arr.iter().sum();
let x = arr
.iter()
.enumerate()
.try_fold((sum - &sum, sum), |(left, right), (idx, x)| {
if left == right - x {
Err(idx)
} else {
Ok((left + x, right - x))
}
});
x.err()
}
#[cfg(test)]
mod tests {
use super::*;
use test_case::test_case;
#[test_case(&[1, 1, 1, 2], 2)]
#[test_case(&[1, 2, 3, 6, 3, 3], 3)]
#[test_case(&[0, 1, 0], 1)]
#[test_case(&[0, 0, 0], 0)]
#[test_case(&[4, 1000, 1, 1, 1, 1], 1)]
fn test_some(arr: &[usize], expected_idx: usize) {
let idx = brutal(arr);
assert_eq!(idx, Some(expected_idx));
}
#[test_case(&[4, 1000, 1, 10, 1, 1])]
#[test_case(&[1, 2, 3, 4, 5])]
fn test_none(arr: &[u32]) {
let idx = brutal(arr);
assert_eq!(idx, None);
}
}
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