976. Largest Perimeter Triangle
Given an array A of positive lengths, return the largest perimeter of a triangle with non-zero area, formed from 3 of these lengths.
If it is impossible to form any triangle of non-zero area, return 0.
Example 1:
Input: [2,1,2] Output: 5
Example 2:
Input: [1,2,1] Output: 0
Example 3:
Input: [3,2,3,4] Output: 10
Example 4:
Input: [3,6,2,3] Output: 8
Note:
3 <= A.length <= 100001 <= A[i] <= 10^6
Rust Solution
struct Solution;
impl Solution {
fn largest_perimeter(mut a: Vec<i32>) -> i32 {
let n = a.len();
a.sort_unstable();
for i in (0..=n - 3).rev() {
if a[i] + a[i + 1] > a[i + 2] {
return a[i] + a[i + 1] + a[i + 2];
}
}
0
}
}
#[test]
fn test() {
let a = vec![2, 1, 2];
assert_eq!(Solution::largest_perimeter(a), 5);
let a = vec![1, 2, 1];
assert_eq!(Solution::largest_perimeter(a), 0);
let a = vec![3, 2, 3, 4];
assert_eq!(Solution::largest_perimeter(a), 10);
let a = vec![3, 6, 2, 3];
assert_eq!(Solution::largest_perimeter(a), 8);
}
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