ARTS #171

Algorithm

本周选择的算法题是：The Number of Weak Characters in the Game。

规则

You are playing a game that contains multiple characters, and each of the characters has two main properties: attack and defense. You are given a 2D integer array properties where properties[i] = [attacki, defensei] represents the properties of the ith character in the game.

A character is said to be weak if any other character has both attack and defense levels strictly greater than this character’s attack and defense levels. More formally, a character i is said to be weak if there exists another character j where attackj > attacki and defensej > defensei.

Return the number of weak characters.

Example 1:

Input: properties = [[5,5],[6,3],[3,6]]
Output: 0
Explanation: No character has strictly greater attack and defense than the other.

Example 2:

Input: properties = [[2,2],[3,3]]
Output: 1
Explanation: The first character is weak because the second character has a strictly greater attack and defense.

Example 3:

Input: properties = [[1,5],[10,4],[4,3]]
Output: 1
Explanation: The third character is weak because the second character has a strictly greater attack and defense.

Constraints:

2 <= properties.length <= 105
properties[i].length == 2
1 <= attacki, defensei <= 105

Solution

impl Solution {
    pub fn number_of_weak_characters(mut properties: Vec<Vec<i32>>) -> i32 {
        properties.sort_unstable_by_key(|key| (key[0], -key[1]));

        let (mut ans, mut min) = (0, i32::min_value());
        for i in (0..properties.len()).rev() {
            if properties[i][1] < min {
                ans += 1;
            }
            min = min.max(properties[i][1]);
        }
        ans
    }
}