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747. Largest Number At Least Twice of Others

题目

You are given an integer array nums where the largest integer is unique.

Determine 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, or return -1 otherwise.

Example 1:

Input: nums = [3,6,1,0]
Output: 1
Explanation: 6 is the largest integer.
For every other number in the array x, 6 is at least twice as big as x.
The index of value 6 is 1, so we return 1.

Example 2:

Input: nums = [1,2,3,4]
Output: -1
Explanation: 4 is less than twice the value of 3, so we return -1.

Example 3:

Input: nums = [1]
Output: 0
Explanation: 1 is trivially at least twice the value as any other number because there are no other numbers.

Constraints:

• 1 <= nums.length <= 50
• 0 <= nums[i] <= 100
• The largest element in nums is unique.

题目大意

给你一个整数数组 nums ，其中总是存在 唯一的 一个最大整数 。请你找出数组中的最大元素并检查它是否 至少是数组中每个其他数字的两倍 。如果是，则返回 最大元素的下标 ，否则返回 -1 。

解题思路

• 简单题。先扫描一遍找到最大值和下标。再扫描一遍检查最大值是否是其他数字的两倍。

代码

package leetcode

func dominantIndex(nums []int) int {
	maxNum, flag, index := 0, false, 0
	for i, v := range nums {
		if v > maxNum {
			maxNum = v
			index = i
		}
	}
	for _, v := range nums {
		if v != maxNum && 2*v > maxNum {
			flag = true
		}
	}
	if flag {
		return -1
	}
	return index
}