rust_test/src/main.rs

enum Operation {
    Add,
    Subtract,
    Multiply,
    Divide,
}
enum Card {
    Int(i32),
    Op(Operation),
}
struct Solution;
impl Solution {
    fn solve(cards: &Vec<Card>) -> bool {
        let mut stack = Vec::new();
        for t in cards.iter() {
            if let Card::Op(op) = t {
                if stack.len() < 2 {
                    return false;
                }
                let b = stack.pop().unwrap() as f64;
                let a = stack.pop().unwrap() as f64;
                let result = match op {
                    Operation::Add => a + b,
                    Operation::Subtract => a - b,
                    Operation::Multiply => a * b,
                    Operation::Divide => {
                        if b == 0f64 {
                            return false;
                        }
                        a / b
                    }
                };
                stack.push(result);
            } else if let Card::Int(num) = t {
                stack.push(*num as f64);
            }
        }
        if stack.len() != 1 {
            return false;
        }
        (24f64 - stack[0]).abs() < 1e-5
    }
    fn dfs(cards: &Vec<i32>, card_objects: &mut Vec<Card>, visited: &mut Vec<bool>) -> bool {
        if card_objects.len() == 7 {
            return Self::solve(card_objects);
        }
        for i in 0..8 {
            if i <= 3 {
                if visited[i] {
                    continue;
                }
                visited[i] = true;
                card_objects.push(Card::Int(cards[i]));
                if Self::dfs(cards, card_objects, visited) {
                    return true;
                }
                card_objects.pop();
                visited[i] = false;
            }
            else {
                let op = match i {
                    4 => Operation::Add,
                    5 => Operation::Subtract,
                    6 => Operation::Multiply,
                    _ => Operation::Divide,
                };
                card_objects.push(Card::Op(op));
                if Self::dfs(cards, card_objects, visited) {
                    return true;
                }
                card_objects.pop();
            }
        }
        false
    }

    pub fn judge_point24(cards: Vec<i32>) -> bool {
        let mut visited = vec![false; 4];
        let mut card_objects = Vec::new();
        for i in 0..4 {
            visited[i] = true;
            card_objects.push(Card::Int(cards[i]));
            for j in 0..4 {
                if visited[j] {
                    continue;
                } else {
                    visited[j] = true;
                    card_objects.push(Card::Int(cards[j]));
                    if Self::dfs(&cards, &mut card_objects, &mut visited) {
                        return true;
                    }
                    card_objects.pop();
                    visited[j] = false;
                }
            }
            card_objects.pop();
            visited[i] = false;
        }
        false
    }
}

fn main() {
    let sl = Solution::judge_point24(vec![3,3,8,8]);
    println!("{:?}", sl);
}