LeetCode:Next Greater Element II

503. Next Greater Element II

Given a circular array (the next element of the last element is the first element of the array), print the Next Greater Number for every element. The Next Greater Number of a number x is the first greater number to its traversing-order next in the array, which means you could search circularly to find its next greater number. If it doesn't exist, output -1 for this number.

Example 1:

Input: [1,2,1]
Output: [2,-1,2]
Explanation: The first 1's next greater number is 2; 
The number 2 can't find next greater number; 
The second 1's next greater number needs to search circularly, which is also 2.

 思路：首先想到最直接的思路就是依次环形搜索，时间复杂度为O(n*n)

vector<int> nextGreaterElements(vector<int>& nums) 
{
    vector<int>r;
    int size = nums.size();
    for (int i = 0; i < size; i++)
    {
        bool exist = false;
        for (int j = (i + 1)%size; j != i; j = (j + 1) % size)
        {
            if (nums[i]<nums[j])
            {
                exist = true;
                r.push_back(nums[j]);
                break;
            }
        }
        if (!exist)
            r.push_back(-1);
    }
    return r;
}

 

 

如果你有任何疑问或新的想法，欢迎在下方评论。