646. Maximum Length of Pair Chain

You are given n pairs of numbers. In every pair, the first number is always smaller than the second number.

Now, we define a pair (c, d) can follow another pair (a, b) if and only if b < c. Chain of pairs can be formed in this fashion.

Given a set of pairs, find the length longest chain which can be formed. You needn't use up all the given pairs. You can select pairs in any order.

Example 1:

Input: [[1,2], [2,3], [3,4]]
Output: 2
Explanation: The longest chain is [1,2] -> [3,4]

Note:

  1. The number of given pairs will be in the range [1, 1000].

Rust Solution

struct Solution;

impl Solution {
    fn find_longest_chain(mut pairs: Vec<Vec<i32>>) -> i32 {
        let n = pairs.len();
        pairs.sort_by_key(|p| p[1]);
        let mut res = 0;
        let mut cur = std::i32::MIN;
        for i in 0..n {
            if cur < pairs[i][0] {
                cur = pairs[i][1];
                res += 1;
            }
        }
        res as i32
    }
}

#[test]
fn test() {
    let pairs = vec_vec_i32![[1, 2], [2, 3], [3, 4]];
    let res = 2;
    assert_eq!(Solution::find_longest_chain(pairs), res);
}

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