#include <iostream> // std::cout, std::endl; #include <algorithm> // std::unique #include <vector> // std::vector void printVec(std::vector<int> &vec) { std::cout << ""; for (auto it = vec.begin(); it != vec.end(); ++it) { std::cout << *it << " "; } std::cout << std::endl; } int main() { std::vector<int> vec = {10,40,40,20,20,30,20,20,40}; std::unique(vec.begin(), vec.end()); printVec(vec); // 10