747. Largest Number At Least Twice of Others

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747. Largest Number At Least Twice of Others

题目描述

In a given integer array nums, there is always exactly one largest element.

Find whether the largest element in the array is at least twice as much as every other number in the array.

If it is, return the index of the largest element, otherwise return -1.

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Example 1:
Input: nums = [3, 6, 1, 0]
Output: 1
Explanation: 6 is the largest integer, and for every other number in the array x,
6 is more than twice as big as x.  The index of value 6 is 1, so we return 1.
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Example 2:
Input: nums = [1, 2, 3, 4]
Output: -1
Explanation: 4 isn't at least as big as twice the value of 3, so we return -1.

Note:
nums will have a length in the range [1, 50].
Every nums[i] will be an integer in the range [0, 99].

题目大意

找出数组内的最大值，并且最大值至少是其他数值的二倍。如果存在，则返回最大值下标，否则返回-1。

解题思路

找出最大值，遍历数组，是否符合题目条件。

代码

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class Solution {
    func dominantIndex(_ nums: [Int]) -> Int {
        guard !nums.isEmpty else { return -1 }
        
        var max = nums.max()!
        var index = -1
        
        for (i, num) in nums.enumerated() where num * 2 > max {
            guard num != max else {
                index = i
                continue
            }
            return -1
        }
        return index
    }
}
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