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4_FindMissingElement.cpp
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4_FindMissingElement.cpp
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/**
There is an array of non-negative integers.
A second array is formed by shuffling the elements of the first array and deleting a random element.
Given these two arrays, find which element is missing in the second array.
*/
#include <map>
#include <vector>
#include <iostream>
#include <algorithm>
#define ALTERNATIVESOLVE 1
uint32_t findDeletedElement(const std::vector<uint32_t> &ogVector, const std::vector<uint32_t> &shuffledVector)
{
#if ALTERNATIVESOLVE
std::map<uint32_t, int> elementMap;
for (const auto &shuffledElement : shuffledVector)
{
++elementMap[shuffledElement];
}
for (const auto &ogElement : ogVector)
{
if (--elementMap[ogElement] != 0)
{
return ogElement;
}
}
return 0;
#else
uint32_t res{0};
for (const auto e : ogVector)
{
res = res ^ e;
}
for (const auto e : shuffledVector)
{
res = res ^ e;
}
// An XOR of all the elements of an array will always return that which has no pair.
return res;
#endif
}
int main()
{
{
const std::vector<uint32_t> originalVector{1, 2, 3, 4, 5, 6};
const std::vector<uint32_t> shuffledVector{2, 1, 3, 6, 4};
std::cout << "Expected value is 5. Got: " << findDeletedElement(originalVector, shuffledVector) << '\n';
}
{
const std::vector<uint32_t> originalVector{1, 2, 1, 1};
const std::vector<uint32_t> shuffledVector{2, 1, 1};
std::cout << "Expected value is 1. Got: " << findDeletedElement(originalVector, shuffledVector) << '\n';
}
return 0;
}