1346. Check If N and Its Double Exist

難度: Easy

類型: Array, Hash Table, Two Pointers, Binary Search, Sorting

C程式下載: 1346.c

前情題要:

檢查陣列中是否有兩個數, 一個數是另一個數的兩倍。

Given an array arr of integers, check if there exist 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: For i = 0 and j = 2, arr[i] == 10 == 2 * 5 == 2 * arr[j]

Example 2:

Input: arr = [3,1,7,11]
Output: false
Explanation: There is no i and j that satisfy the conditions.

 

Constraints:

• 2 <= arr.length <= 500
• -103 <= arr[i] <= 103

思考方式:

1. 每個數跟它後面的每一個數字比較, 是否為該數字的兩倍或二分之一。

複雜度思考:

Time Complexity: O( 0.5*N^2 ) 

Space Complexity: O( x )

結果:

Runtime: 0 ms, Beats: 100%

Memory: 8.47 MB, Beats: 29.94%

Accepted

112 / 112 testcases passed

tendchen

submitted at Apr 29, 2025 12:55

Runtime

0ms

Beats100.00%

Analyze Complexity

Memory

8.47MB

Beats29.94%

Analyze Complexity

Code

C

bool checkIfExist(int* arr, int arrSize) {
    int i,j;
    for (i=0;i<arrSize;i++)
    {
        for (j=i+1;j<arrSize;j++)
        {
            if ((arr[i]==arr[j]*2)||(arr[j]==arr[i]*2))
                return true;
        }
    }
    return false;
}