Find Peak Element Using Binary Search in DSA C++ - Build from Scratch

Find Peak Element Using Binary Search

📖 Scenario: Imagine you have a list of numbers representing heights of hills along a trail. You want to find a hill that is taller than its neighbors, called a peak.

🎯 Goal: Build a program that finds a peak hill using a fast method called binary search.

📋 What You'll Learn

Create a vector called heights with exact values

Create two integer variables left and right for binary search boundaries

Use a while loop to apply binary search logic

Print the index of a peak element found

💡 Why This Matters

🌍 Real World

Finding peaks is useful in signal processing, stock price analysis, and terrain mapping where local maximum points matter.

💼 Career

Binary search and peak finding are common in technical interviews and real-world software that needs fast data analysis.

1

Create the heights vector

Create a std::vector<int> called heights with these exact values: 1, 3, 20, 4, 1, 0

DSA C++

#include 
#include 

int main() {
    // Create the heights vector
    // Your code here
}

Hint

Use std::vector<int> heights = {1, 3, 20, 4, 1, 0}; to create the vector.

2

Set binary search boundaries

Create two integer variables called left and right. Set left to 0 and right to heights.size() - 1

DSA C++

#include 
#include 

int main() {
    std::vector heights = {1, 3, 20, 4, 1, 0};
    // Set left and right boundaries
    // Your code here
}

Hint

Use int left = 0; and int right = heights.size() - 1;.

3

Apply binary search to find a peak

Use a while loop with condition left < right. Inside the loop, create mid as left + (right - left) / 2. If heights[mid] < heights[mid + 1], set left = mid + 1, else set right = mid

DSA C++

#include 
#include 

int main() {
    std::vector heights = {1, 3, 20, 4, 1, 0};
    int left = 0;
    int right = heights.size() - 1;

    // Use binary search to find peak
    // Your code here
}

Hint

Use a while loop and update left or right based on comparing heights[mid] and heights[mid + 1].

4

Print the peak element index

Print the value of left using std::cout to show the index of a peak element

DSA C++

#include 
#include 

int main() {
    std::vector heights = {1, 3, 20, 4, 1, 0};
    int left = 0;
    int right = heights.size() - 1;

    while (left < right) {
        int mid = left + (right - left) / 2;
        if (heights[mid] < heights[mid + 1]) {
            left = mid + 1;
        } else {
            right = mid;
        }
    }

    // Print the peak index
    // Your code here
}

Hint

Use std::cout << left << std::endl; to print the peak index.