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162. 寻找峰值 ​

为保证权益，题目请参考 162. 寻找峰值(From LeetCode).

解决方案1 ​

CPP ​

C++
//
// Created by lenovo on 2020-09-18.
//

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

// 顺序法
//class Solution {
//public:
//    int findPeakElement(vector<int> &nums) {
//        for(int i=0;i<nums.size()-1;i++){
//            if(nums[i] > nums[i+1]){
//                return i;
//            }
//        }
//        return nums.size()-1;
//    }
//};

class Solution {
private:
    int helper(vector<int> &nums, int l, int r) {
        if (l == r) {
            return l;
        }

        int m = (l + r) / 2;
        if (nums[m] > nums[m + 1]) {
            return helper(nums, l, m);
        } else {
            return helper(nums, m+1, r);
        }
    }

public:
    // TODO: Binary Finder
    int findPeakElement(vector<int> &nums) {
        return this->helper(nums, 0, nums.size() - 1);
    }
};

void runTest(){
    vector<int> vec;
    vec.push_back(1);
    vec.push_back(2);
    vec.push_back(3);
    vec.push_back(1);

    Solution so;
    cout << so.findPeakElement(vec) << endl;
}

int main() {
    runTest();
    return 0;
}

Python ​

python
# 162. 寻找峰值
# https://leetcode-cn.com/problems/find-peak-element/


################################################################################

from typing import List


class Solution:
    def findPeakElement(self, nums: List[int]) -> int:
        if len(nums) == 1:
            return 0

        if nums[0] > nums[1]:
            return 0

        if nums[len(nums) - 1] > nums[len(nums) - 2]:
            return len(nums) - 1

        l = 1
        r = len(nums) - 2
        while l <= r:
            m = (l + r) // 2
            if nums[m] < nums[m + 1]:
                l = m + 1
            else:
                if nums[m] < nums[m - 1]:
                    r = m - 1
                else:
                    return m


################################################################################


if __name__ == "__main__":
    solution = Solution()
    print(solution.findPeakElement([2, 3, 1]))