Question

How to check whether a vector is sorted in C++

Answer 1

#include <algorithm>   // std::is_sorted
#include <iostream>    // std::cout
#include <vector>      // std::vector

// ------------------------------------------------------------
// Function: isVectorSorted
// Purpose:  Check whether a vector is sorted in non‑decreasing order.
// Notes:
//   - Uses std::is_sorted, which runs in O(n) time.
//   - std::is_sorted is idiomatic, efficient, and expressive.
// ------------------------------------------------------------
bool isVectorSorted(const std::vector<int>& vec) {
    // std::is_sorted returns true if each element is <= the next.
    return std::is_sorted(vec.begin(), vec.end());
}

int main() {
    std::vector<int> data = {1, 2, 3, 5, 8, 13};

    bool sorted = isVectorSorted(data);

    std::cout << "Vector is "
              << (sorted ? "sorted" : "NOT sorted")
              << std::endl;
}



/*
run:

Vector is sorted

*/

 

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