解小学一年级数学题

亲戚的儿子发来一道数学题，于是草稿打了很久也没解决，后面干脆直接用程序跑。分别用go和rust。跑出来有4种解。不得不说现在小学题已经不是当年那样的了。

package main

import "fmt"

func solve(nums []int, c chan []int) {
    dfs(nums, 0, []int{}, c)
    close(c)
}

func dfs(nums []int, depth int, res []int, c chan []int) {
    if depth == len(nums) {
        if res[0]+res[1] == 13 &&
            res[1]+res[2]+res[3] == 13 &&
            res[3]+res[4]+res[5] == 13 &&
            res[5]+res[6]+res[7] == 13 &&
            res[7]+res[8] == 13 {
            c <- res
        }
        return
    }
    for i := 0; i < len(nums); i++ {
        if !contains(res, nums[i]) {
            dfs(nums, depth+1, append(res, nums[i]), c)
        }
    }
}

func contains(nums []int, n int) bool {
    for _, num := range nums {
        if num == n {
            return true
        }
    }
    return false
}

func main() {
    nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
    c := make(chan []int)

    go solve(nums, c)

    for res := range c {
        fmt.Println(res)
    }
}

fn solve(nums: &[i32], c: &mut std::sync::mpsc::Sender<Vec<i32>>) {
    dfs(nums, 0, &mut vec![], c);
}

fn dfs(nums: &[i32], depth: usize, mut res: &mut Vec<i32>, c: &mut std::sync::mpsc::Sender<Vec<i32>>) {
    if depth == nums.len() {
        if res[0] + res[1] == 13 &&
            res[1] + res[2] + res[3] == 13 &&
            res[3] + res[4] + res[5] == 13 &&
            res[5] + res[6] + res[7] == 13 &&
            res[7] + res[8] == 13 {
            c.send(res.clone()).expect("发送结果失败!");
        }
        return;
    }
    for i in nums {
        if !res.contains(i) {
            res.push(*i);
            dfs(nums, depth + 1, &mut res, c);
            res.pop();
        }
    }
}

fn main() {
    let nums = [1, 2, 3, 4, 5, 6, 7, 8, 9];
    let (mut tx, rx) = std::sync::mpsc::channel();

    std::thread::spawn(move || {
        solve(&nums, &mut tx);
        drop(tx);
    });

    for res in rx.iter() {
        println!("{:?}", res);
    }
}