LeetCode/162.cpp at master · nitin-maharana/LeetCode · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
/*
 * Written by Nitin Kumar Maharana
 * nitin.maharana@gmail.com
 */

//O(logN)
class Solution {
    void findPeakElement(vector<int>& nums, int l, int r, int& index)
    {
        if(l > r)
            return;

        int mid = l + ((r - l) / 2);

        if(nums[mid] > nums[mid-1] && nums[mid] > nums[mid+1])
        {
            index = mid;
            return;
        }

        findPeakElement(nums, l, mid-1, index);
        findPeakElement(nums, mid+1, r, index);

        return;
    }
public:
    int findPeakElement(vector<int>& nums) {
        int len = nums.size();

        if(len == 1)
            return 0;

        if(1 < len && nums[0] > nums[1])
            return 0;

        if(len-2 >= 0 && nums[len-1] > nums[len-2])
            return len-1;

        int index = 0;

        findPeakElement(nums, 1, len-2, index);

        return index;
    }
};

//O(N)
class Solution {
public:
    int findPeakElement(vector<int>& nums) {
        int len = nums.size();

        if(len == 1)
            return 0;

        if(1 < len && nums[0] > nums[1])
            return 0;

        if(len-2 >= 0 && nums[len-1] > nums[len-2])
            return len-1;

        for(int i = 1; i < len-1; i++)
            if(nums[i] > nums[i-1] && nums[i] > nums[i+1])
                return i;
    }
};