README_EN.md

747. Largest Number At Least Twice of Others

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Description

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

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.

 

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.

Example 2:

Input: nums = [1,2,3,4]
Output: -1
Explanation: 4 is not at least as big as twice the value of 3, so we return -1.

 

Constraints:

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

Solutions

Python3

class Solution:
    def dominantIndex(self, nums: List[int]) -> int:
        mx = mid = 0
        ans = -1
        for i, v in enumerate(nums):
            if v > mx:
                mid, mx = mx, v
                ans = i
            elif v > mid:
                mid = v
        return ans if mx >= 2 * mid else -1

Java

class Solution {
    public int dominantIndex(int[] nums) {
        int mx = 0, mid = 0;
        int ans = -1;
        for (int i = 0; i < nums.length; ++i) {
            if (nums[i] > mx) {
                mid = mx;
                mx = nums[i];
                ans = i;
            } else if (nums[i] > mid) {
                mid = nums[i];
            }
        }
        return mx >= mid * 2 ? ans : -1;
    }
}

C++

class Solution {
public:
    int dominantIndex(vector<int>& nums) {
        int mx = 0, mid = 0;
        int ans = 0;
        for (int i = 0; i < nums.size(); ++i)
        {
            if (nums[i] > mx)
            {
                mid = mx;
                mx = nums[i];
                ans = i;
            }
            else if (nums[i] > mid) mid = nums[i];
        }
        return mx >= mid * 2 ? ans : -1;
    }
};

Go

func dominantIndex(nums []int) int {
	mx, mid := 0, 0
	ans := 0
	for i, v := range nums {
		if v > mx {
			mid, mx = mx, v
			ans = i
		} else if v > mid {
			mid = v
		}
	}
	if mx >= mid*2 {
		return ans
	}
	return -1
}

JavaScript

/**
 * @param {number[]} nums
 * @return {number}
 */
var dominantIndex = function (nums) {
    let mx = 0,
        mid = 0;
    let ans = 0;
    for (let i = 0; i < nums.length; ++i) {
        if (nums[i] > mx) {
            mid = mx;
            mx = nums[i];
            ans = i;
        } else if (nums[i] > mid) {
            mid = nums[i];
        }
    }
    return mx >= mid * 2 ? ans : -1;
};

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