Question

How to find the index of N in a sorted vector if N is not present, return the index where it would be in C++

Answer 1

#include <iostream>
#include <vector>
#include <algorithm> // for std::lower_bound

// Function to find the index where N would be inserted
int findInsertPosition(const std::vector<int>& arr, int N) {
    auto it = std::lower_bound(arr.begin(), arr.end(), N);
    
    return it - arr.begin(); // Return the index
}

int main() {
    std::vector<int> arr = {1, 3, 5, 7, 8, 9, 12, 15}; // Sorted array
    int N = 6; // Element to find or insert

    int index = findInsertPosition(arr, N);

    std::cout << "Index where " << N << " is OR would be: " << index << std::endl;
}



/*
run:

Index where 6 is OR would be: 3

*/

 

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Answer 2

#include <iostream>
#include <vector>

// Function to find the index and check existence
void findOrInsertPosition(const std::vector<int>& arr, int N) {
    auto it = std::lower_bound(arr.begin(), arr.end(), N);
    int index = it - arr.begin();

    if (it != arr.end() && *it == N)
        std::cout << "Found at index: " << index << std::endl;
    else
        std::cout << "Index where " << N << " would be: " << index << std::endl;
}

int main() {
    std::vector<int> arr = {1, 3, 5, 7, 8, 9, 12, 15}; // Sorted array
    int N = 6; // Element to find or insert

    findOrInsertPosition(arr, N);    
    findOrInsertPosition(arr, 9);
}



/*
run:

Index where 6 would be: 3
Found at index: 5

*/

 

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