first_non_repeating_int.cpp

/*
 * Given an array of integers, determine the first non repeating integer in the array.
 */

#include<iostream>
#include<map>


int nonRepeating(int *arr, int size){
	std::map<int, int> m;
	std::map<int,int>::iterator it;
	for(int i = 0; i < size; ++i){
		it = m.find(arr[i]);
		if( it != m.end()){
			m[arr[i]] = ++(it->second);
		}
		else{
			m[arr[i]] = 1;
		}
	}

	for(int i = 0; i < size; ++i){
		it = m.find(arr[i]);
		if( it != m.end()){
			if(it->second == 1)
				return arr[i];
		}
	}
	return -1;

}

int main(){
	int size;
	int *arr;
	std::cout<<"Enter size:";
	std::cin>>size;
	arr = new int[size];
	std::cout<<"Enter contents of array:";
	for(int i = 0; i < size; ++i){
		std::cin>>arr[i];
	}
	std::cout<<"First Non repeating integer in array:"<< nonRepeating(arr,size)<<std::endl;
	delete[] arr;
	return 0;
}