Question

How to remove all occurrences of a value in array of integers with C++

Answer 1

#include <iostream>
#include <vector>

void printVector(std::vector<int> const &v) {
    for (auto const &n: v) {
        std::cout << n << " ";
    }
}

int removeElement(std::vector<int>& vec, int val) {
    int i = 0, end = vec.size() - 1;

    while (i <= end) {
        if (vec[i] == val) {
            std::swap(vec[i], vec[end]);
            end--;
            vec.pop_back();
        }
        else {
            i++;
        }
    }
    
    return vec.size();
}
 
int main() {
    std::vector<int> vec{ 1, 3, 8, 23, 8, 99, 8, 100, 7 };
    int value = 8;
    
    removeElement(vec, value);
 
    printVector(vec);
}
 
 
 
/*
run:
 
1 3 7 23 100 99 
 
*/

 

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Answer 2

#include <iostream>    
#include <algorithm>   
 
int main () {
  int arr[] = {1, 3, 8, 23, 8, 99, 8, 100, 7};     
  int *end = arr + sizeof(arr) / sizeof(int); 
  int value = 8;
 
  end = std::remove(arr, end, value);         
                                                  
  for (int *p = arr; p != end; p++) {
        std::cout << *p << ' ';
  }
}
 
 
 
/*
run:
 
1 3 23 99 100 7 
 
*/

 

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Answer 3

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

std::vector<int> removeElements(std::vector<int>& arr, int value) {
    int index = 0;
    
    for (int i = 0; i < arr.size(); i++) {
        if (arr[i] != value) {
            arr[index++] = arr[i];
        }
    }
    
    arr.resize(index);
    
    return arr;
}

int main() {
    std::vector<int> array = {1, 3, 8, 23, 8, 99, 8, 100, 7};
    int value = 8;
    
    removeElements(array, value);
    
    for (int num : array) {
        std::cout << num << " ";
    }
}

 
 
/*
run:
 
1 3 23 99 100 7 
 
*/

 

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