Array algorithms in C++ STL

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Hello everyone!

I want to offer you a blog about the STL of C++11, a few weeks ago I was reading interesting information about this topic in GeeksforGeeks, and today I decided to share this information through this blog for all those interested. In advance, I want to thank all those who pay attention and interest to this blog, and thank any comments about it (positive or negative). Well, let's start now.

I will start with some array algorithms in the C++11 STL, which I did not know before and that can have a very interesting use, depending on the problem.

Array algorithms: these algorithms operate on an array and are useful in saving time during coding and hence useful in competitive programming as well.

all_of(): this function operates on whole range of array elements and can save time to run a loop to check each element one by on. It checks for a given property on every element and returns true when each element in range satisfies specified property, else returns false.

Code

#include "bits/stdc++.h"
using namespace std;

int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  // initializing array
  vector<int> a = {1, 2, 3, 4, 5, -6};

  // checking if all elements are odds
  bool allOdds = all_of(a.begin(), a.end(), [](int x) { 
    return x % 2 != 0; 
  });

  if (allOdds) {
    cout << "All are odds numbers\n";
  } else {
    cout << "All are not odds numbers\n";
  }

  // output:
  // All are not odds numbers
}

any_of(): this function checks for a given range if there’s even one element satisfying a given property mentioned in function. Returns true if at least one element satisfies the property, else returns false.

Code

#include "bits/stdc++.h"
using namespace std;

int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  // initializing array
  vector<int> a = {1, 2, 3, 4, 5, -6};

  // checking if any element is negative.
  bool anyNegative = any_of(a.begin(), a.end(), [](int x) {
    return x < 0;
  });

  if (anyNegative) {
    cout << "There are exists a negative element\n";
  } else {
    cout << "All are positive elements\n";
  }

  // output:
  // There are exists a negative element
}

none_of(): this function returns true if none of element satisfies the given condition, else returns false.

Code

#include "bits/stdc++.h"
using namespace std;

int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  // initializing array
  vector<int> a = {1, 2, 3, 4, 5, -6};

  // checking if no element is negative.
  bool noNegative = none_of(a.begin(), a.end(), [](int x) {
    return x < 0; 
  });

  if (noNegative) {
    cout << "No negative elements\n";
  } else {
    cout << "There are negative element\n";
  }

  // output:
  // There are negative element
}

iota(): this function is used to assign continuous values to array.

Code

#include "bits/stdc++.h"
using namespace std;

int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  // initializing array
  vector<int> a(6, 0);

  // using iota() to assign values
  iota(a.begin(), a.end(), 20);

  // displaying the new array
  cout << "The new array after assigning values is: ";

  for (auto &x: a) {
    cout << x << " \n"[&x == &a.back()];
  }

  // output:
  // The new array after assigning values is: 20 21 22 23 24 25
}

accumulate(): this function returns the sum of all the values lying in a range between [first, last) with the variable sum.

Code

Thank you to all

Comments (7)

Write comment?

bool_everything_zero

2 years ago, # |

is it applicable for c++14???????

→ Reply

EduardoBrito

2 years ago, # ^ |

Yes, it is.

KhozmoS

Thanks for share! I have a question the time complexity of those functions is linear?

FelixDzerzhinsky

all_of, any_of, none_of, accumulate, iota — O(n)

copy_n — O(cnt)

p.s. https://en.cppreference.com/w/cpp/algorithm/copy_n

Behind_Y0u

4 months ago, # |

what does the following do?

ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

Kumar_yog

4 months ago, # ^ |

https://stackoverflow.com/questions/31162367/significance-of-ios-basesync-with-stdiofalse-cin-tienull

You can look in the above link

n00brekt

← Rev. 5 →

I tried implementing them in python and here are the codes except for none_of but you can do it using all() and not keywords.

all_of

def main():
    arr = [1,2,3,4]
    ans = all([i & 1 for i in arr])
    if ans:
        print("All numbers are odd")
    else:
        print("All numbers are not odd")

any_off

def main():
    arr = [1,2,3,4]
    ans = any([i & 1 for i in arr])
    if ans:
        print("There exists a odd number")
    else:
        print("No odd number exists")

copy_n

def main():
    arr = [1,2,3,4]
    arr1 = arr.copy()
    print(arr1) # [1,2,3,4]

iota

def main():
    n=10
    arr = list(range(1, n + 1))
    print(arr) # [1,2,3,4,5,6,7,8,9,10]

accumulate

def main():
    import itertools
    import operator
    arr=[1,2,3,4,5]
    result = list(itertools.accumulate(arr, operator.mul)) # [1,2,6,24,120]

More Operators — Link

EduardoBrito's blog

include "bits/stdc++.h"