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Easy
1227
Biweekly Contest 106 Q1
Hash Table
Math

2729. Check if The Number is Fascinating

中文文档

Description

You are given an integer n that consists of exactly 3 digits.

We call the number n fascinating if, after the following modification, the resulting number contains all the digits from 1 to 9 exactly once and does not contain any 0's:

  • Concatenate n with the numbers 2 * n and 3 * n.

Return true if n is fascinating, or false otherwise.

Concatenating two numbers means joining them together. For example, the concatenation of 121 and 371 is 121371.

 

Example 1:

Input: n = 192
Output: true
Explanation: We concatenate the numbers n = 192 and 2 * n = 384 and 3 * n = 576. The resulting number is 192384576. This number contains all the digits from 1 to 9 exactly once.

Example 2:

Input: n = 100
Output: false
Explanation: We concatenate the numbers n = 100 and 2 * n = 200 and 3 * n = 300. The resulting number is 100200300. This number does not satisfy any of the conditions.

 

Constraints:

  • 100 <= n <= 999

Solutions

Solution 1

Python3

class Solution:
    def isFascinating(self, n: int) -> bool:
        s = str(n) + str(2 * n) + str(3 * n)
        return "".join(sorted(s)) == "123456789"

Java

class Solution {
    public boolean isFascinating(int n) {
        String s = "" + n + (2 * n) + (3 * n);
        int[] cnt = new int[10];
        for (char c : s.toCharArray()) {
            if (++cnt[c - '0'] > 1) {
                return false;
            }
        }
        return cnt[0] == 0 && s.length() == 9;
    }
}

C++

class Solution {
public:
    bool isFascinating(int n) {
        string s = to_string(n) + to_string(n * 2) + to_string(n * 3);
        sort(s.begin(), s.end());
        return s == "123456789";
    }
};

Go

func isFascinating(n int) bool {
	s := strconv.Itoa(n) + strconv.Itoa(n*2) + strconv.Itoa(n*3)
	cnt := [10]int{}
	for _, c := range s {
		cnt[c-'0']++
		if cnt[c-'0'] > 1 {
			return false
		}
	}
	return cnt[0] == 0 && len(s) == 9
}

TypeScript

function isFascinating(n: number): boolean {
    const s = `${n}${n * 2}${n * 3}`;
    return s.split('').sort().join('') === '123456789';
}

Rust

impl Solution {
    pub fn is_fascinating(n: i32) -> bool {
        let s = format!("{}{}{}", n, n * 2, n * 3);

        let mut cnt = vec![0; 10];
        for c in s.chars() {
            let t = (c as usize) - ('0' as usize);
            cnt[t] += 1;
            if cnt[t] > 1 {
                return false;
            }
        }

        cnt[0] == 0 && s.len() == 9
    }
}

Solution 2

Rust

use std::collections::HashMap;

impl Solution {
    pub fn is_fascinating(mut n: i32) -> bool {
        let mut i = n * 2;
        let mut j = n * 3;

        let mut hash = HashMap::new();

        while n != 0 {
            let cnt = hash.entry(n % 10).or_insert(0);
            *cnt += 1;
            n /= 10;
        }

        while i != 0 {
            let cnt = hash.entry(i % 10).or_insert(0);
            *cnt += 1;
            i /= 10;
        }

        while j != 0 {
            let cnt = hash.entry(j % 10).or_insert(0);
            *cnt += 1;
            j /= 10;
        }

        for k in 1..=9 {
            if !hash.contains_key(&k) || hash[&k] > 1 {
                return false;
            }
        }

        !hash.contains_key(&0)
    }
}