Given two arrays, the task is that we find numbers which are present in first array, but not present in the second array, using STL in C++
Examples:
Input: a[] = {1, 2, 3, 4, 5, 10}, b[] = {2, 3, 1, 0, 5}
Output: 4 10
Input:a[] = {4, 3, 5, 9, 11}, b[] = {4, 9, 3, 11, 10};
Output: 5
Approach: In STL, the set_difference() method can be used to find the ‘A-B’ where A is the first array and B is the second array.
Syntax:
OutputIterator set_difference (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result);
Below is the implementation of the above approach:
// C++ simple program to // find elements which are // not present in second array #include <bits/stdc++.h> using namespace std; // Function for finding // elements which are there // in a[] but not in b[]. void findMissing(int a[], int b[], int n, int m) { // Declare a vector to store the result vector<int> v(n + m); // And an iterator to traverse the vector vector<int>::iterator it; // Sort the given arrays sort(a, a + n); sort(b, b + m); // Find the elements in a[] // which are not in b[] it = set_difference(a, a + n, b, b + m, v.begin()); // Now resize the vector to the existing count v.resize(it - v.begin()); // Print the results cout << "The elements in a[]" << " which are not in b[]:\n"; for (it = v.begin(); it != v.end(); ++it) cout << *it << " "; cout << endl; } // Driver code int main() { int a[] = { 1, 2, 6, 3, 4, 5 }; int b[] = { 2, 4, 3, 1, 0 }; int n = sizeof(a) / sizeof(a[0]); int m = sizeof(b) / sizeof(b[1]); findMissing(a, b, n, m); return 0; } |
The elements in a[] which are not in b[]: 5 6
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