1346. Check If N and Its Double Exist

題目敘述

Given an array arr of integers, check if there exists two integers N and M such that N is the double of M ( i.e. N = 2 * M).

More formally check if there exists two indices i and j such that :

i != j
0 <= i, j < arr.length
arr[i] == 2 * arr[j]

Example 1:

Input: arr = [10,2,5,3]
Output: true
Explanation: N = 10 is the double of M = 5,that is, 10 = 2 * 5.

Example 2:

Input: arr = [7,1,14,11]
Output: true
Explanation: N = 14 is the double of M = 7,that is, 14 = 2 * 7.

Example 3:

Input: arr = [3,1,7,11]
Output: false
Explanation: In this case does not exist N and M, such that N = 2 * M.

Constraints:

2 <= arr.length <= 500
-10^3 <= arr[i] <= 10^3

Hint 1:

Loop from i = 0 to arr.length, maintaining in a hashTable the array elements from [0, i - 1].

Hint 2:

On each step of the loop check if we have seen the element 2 * arr[i] so far or arr[i] / 2 was seen if arr[i] % 2 == 0.

題目翻譯

解法解析

解法範例

Go

func checkIfExist(arr []int) bool {
    seen := make(map[float64]bool)
    for _, v := range arr {
        V := float64(v)
        if seen[V*2.0] || seen[V/2.0] {
            return true
        }
        seen[V] = true
    }
    return false
}

JavaScript

/**
 * @param {number[]} arr
 * @return {boolean}
 */
var checkIfExist = function (arr) {
    const seen = new Set();
    for (const value of arr) {
        if (seen.has(value * 2) || seen.has(value / 2)) {
            return true;
        }
        seen.add(value);
    }
    return false;
};

Kotlin

class Solution {
    fun checkIfExist(arr: IntArray): Boolean {
        val seen = hashSetOf<Int>()
        arr.forEach { num ->
            if (seen.contains(num * 2)) return true
            if (num % 2 == 0 && seen.contains(num / 2)) return true
            seen.add(num)
        }
        return false
    }
}

PHP

class Solution
{

    /**
     * @param Integer[] $arr
     * @return Boolean
     */
    function checkIfExist($arr)
    {
        $map = [];
        foreach ($arr as $val) {
            if (isset($map[$val * 2]) || ($val % 2 == 0 && isset($map[$val / 2]))) {
                return true;
            }
            $map[$val] = true;
        }
        return false;
    }
}

Python

class Solution:
    def checkIfExist(self, arr: List[int]) -> bool:
        seen = set(arr)
        for value in arr:
            if 2 * value in seen or value / 2 in seen:
                return True
            seen.add(value)
        return False

Rust

impl Solution {
    pub fn check_if_exist(arr: Vec<i32>) -> bool {
        let mut nums = std::collections::HashSet::new();

        for num in arr.into_iter() {
            if ((num as f32 / 2 as f32).fract() == 0.0 && nums.contains(&(num / 2))) || nums.contains(&(num * 2)) {
                return true
            }
            nums.insert(num);
        }

        false
    }
}

Swift

class Solution {
    func checkIfExist(_ arr: [Int]) -> Bool {
        var seen = Set<Int>()
        for num in arr {
            if seen.contains(num * 2) || (num % 2 == 0 && seen.contains(num / 2)) {
                return true
            }
            seen.insert(num)
        }
        return false
    }
}

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1346. Check If N and Its Double Exist

題目敘述

題目翻譯

解法解析

解法範例

Go

JavaScript

Kotlin

PHP

Python

Rust

Swift

Command Palette

Comments

LeetCode Solution

LeetCode Solution, Easy, 88. Merge Sorted Array

More from this blog

1346. Check If N and Its Double Exist

題目敘述

題目翻譯

解法解析

解法範例

Go

JavaScript

Kotlin

PHP

Python

Rust

Swift