Problem:
Score : 500 points

Problem Statement

Given are N integers A_1,\ldots,A_N.

We will choose exactly K of these elements. Find the maximum possible product of the chosen elements.

Then, print the maximum product modulo (10^9+7), using an integer between 0 and 10^9+6 (inclusive).

Constraints

1 \leq K \leq N \leq 2\times 10^5

|A_i| \leq 10^9

Input

Input is given from Standard Input in the following format:

N K
A_1 \ldots A_N

Output

Print the maximum product modulo (10^9+7), using an integer between 0 and 10^9+6 (inclusive).

Sample Input 1

4 2
1 2 -3 -4

Sample Output 1

12

The possible products of the two chosen elements are 2, -3, -4, -6, -8, and 12, so the maximum product is 12.

Sample Input 2

4 3
-1 -2 -3 -4

Sample Output 2

1000000001

The possible products of the three chosen elements are -24, -12, -8, and -6, so the maximum product is -6.

We print this value modulo (10^9+7), that is, 1000000001.

Sample Input 3

2 1
-1 1000000000

Sample Output 3

1000000000

The possible products of the one chosen element are -1 and 1000000000, so the maximum product is 1000000000.

Sample Input 4

10 10
1000000000 100000000 10000000 1000000 100000 10000 1000 100 10 1

Sample Output 4

999983200

Be sure to print the product modulo (10^9+7).

Solution in Rust (1.42.0) (judge verdict: Runtime Error)

use std::cmp::*;
use std::collections::*;
use std::io::*;
use std::str::FromStr;
fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}
fn main() {
    let n: usize = read();
    let MOD = 1000000007;
    let k: usize = read();
    let mut a: Vec<i64> = (0..n).map(|_| read()).collect();
    let mut pos: Vec<i64> = Vec::new();
    let mut neg: Vec<i64> = Vec::new();
    let mut ans: i64 = 1;
    for i in 0..n {
        if a[i] >= 0 {
            pos.push(a[i]);
        }
        if a[i] < 0 {
            neg.push(a[i]);
        }
        if k == n {
            ans %= MOD;
            ans *= a[i] % MOD;
        }
    }
    if k == n {
        println!("{}", ans);
    } else {
        let pos_sum = pos.len();
        let neg_sum = neg.len();
        let mut pos_idx: usize = 0;
        let mut neg_idx: usize = 0;
        if neg_sum == n && k % 2 == 1 {
            let mut v: Vec<i64> = Vec::new();
            for _i in neg {
                v.push(_i);
            }
            for _i in pos {
                v.push(_i);
            }
            v.sort();
            for i in 0..k {
                ans = (ans * (v[i] % MOD)) % MOD;
            }
            ans %= MOD;
            ans *= -1;
            println!("{}", ans);
        } else {
            pos.sort();
            pos.reverse();
            neg.sort();
            let mut i = 0;
            while i < k {
                if i == k - 1 {
                    ans = (ans * (pos[pos_idx] % MOD)) % MOD;
                } else {
                    let mut v0 = -1e18 as i64;
                    let mut v1 = v0;
                    if pos_idx < pos_sum {
                        v0 = pos[pos_idx] * pos[pos_idx + 1];
                    }
                    if neg_idx + 1 < neg_sum {
                        v1 = neg[neg_idx] * neg[neg_idx + 1];
                    }
                    if v0 > v1 {
                        v0 %= MOD;
                        pos_idx += 2;
                        ans = (ans * (v0 % MOD)) % MOD;
                    }else{
                        v1 %= MOD;
                        neg_idx += 2;
                        ans = (ans * (v1 % MOD)) % MOD;
                    }
                    i += 2;
                }
            }
            println!("{}",ans);
        }
    }
}