747. Largest Number At Least Twice of Others

static int wing=[]()
{
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();

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

扫描一遍，找出最大和第二大的就行了