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JP Morgan Interview Question for Field Saless






Comment hidden because of low score. Click to expand.
1
of 1 vote

for ( it=xmap.begin(), int i=0; it != xmap.end(); it++, i++ )
{

if ( i % 2)
{

mymap.erase (it);

}
}

- topofmyhead July 10, 2011 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 votes

incorrect, code below works

#include <iterator>
#include <map>
#include <iostream>

typedef std::map<int,int>::iterator m_t;

int main()
{
    std::map<int,int> m;

    m[1] = 1; m[2] = 2; m[3] = 3; m[4] = 4;
    m[5] = 5; m[6] = 6; m[7] =7; m[8]=8;m[9]=9;
    m[10] = 10; m[11]=11;

    m_t it = m.begin();
    for(; it != m.end(); ++it) m.erase(it++);

    it = m.begin();
    for(; it != m.end(); ++it) {
	std::cout << it->first << " , " << it->second << std::endl;
    }
}

- joe August 24, 2013 | Flag
Comment hidden because of low score. Click to expand.
0
of 0 votes

This should be wrong since when you erase(it), it will automatically point to next element.
for ( it=xmap.begin(), int i=0; it != xmap.end(); i++ )
{

if ( i % 2)
{
mymap.erase (it);
} else
it ++;
}

- bowen November 24, 2014 | Flag
Comment hidden because of low score. Click to expand.
1
of 1 vote

TestMap::iterator iter = test.begin();
int index = 1;
while(iter != test.end())
{
if (index % 2 == 0) iter = test.erase(iter);
else ++iter;
index++;
}

- xiaofeng.ustc February 02, 2012 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

Void eraseFunction(map<int,int> &x)
{
x.clear();
}

- prime July 10, 2011 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

to erase every other elements, not every elements!

- Itcecsa July 10, 2011 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

Void eraseFunction(map<int,int> &x)
{
       for(map<int,int>::iterator it = x.begin(); it != x.end(); ++it)
       {
            x.erase(it++);
       }
       
}

- Ram July 27, 2011 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 votes

void remove_mp_odd_index_elements(map<int,int>& a_map)
{
    if( a_map.size() <= 1 )
        return;

    int elems_to_erase = a_map.size() / 2;
    int k = 1;
    map<int,int>::iterator it;
    while( k <= elems_to_erase )
    {
        it = a_map.begin();
        for(int j = 1; j<=k; j++)
            it++;
        a_map.erase(it); // an erase invalidates the iterator
        k++;
    }
}

void remove_mp_even_index_elements(map<int,int>& a_map)
{
    if( a_map.size() == 1 )
    {
        a_map.clear();
        return;
    }
    else if( a_map.size() == 2 ){
        a_map.erase(a_map.begin());
        return;
    }

    int elems_to_erase = a_map.size() / 2 + 1;
    int k = 1;
    map<int,int>::iterator it;
    while( k <= elems_to_erase )
    {
        it = a_map.begin();
        for(int j = 1; j<k; j++)
            it++;
        a_map.erase(it); // an erase invalidates the iterator
        k++;
    }
}
# I think that an "erase" invalidates all iterators 
# attached on a container. Thus begin() and/or end must be 
# called in order to have a valid set of iterators and 
# remove the correct elements.

- Thanasis September 11, 2011 | Flag
Comment hidden because of low score. Click to expand.
0
of 0 vote

erasing an element of map in for loop erases every alternative element.

map<int, int> mymap;

for(map<int, int>::iterator it = mymap.begin(); it != mymap.end(); ++it )
{
mymap.erase(it);
}

ig mymap have 10 element, above code erases only 5

- naveen November 01, 2011 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 votes

Wrong Answer. Dead loop.

- Anonymous October 02, 2012 | Flag
Comment hidden because of low score. Click to expand.
0
of 0 vote

void eraseFunction(map<int,int> &x)
{
map<int,int>::iterator k;
for(map<int,int>::iterator it = x.begin(); it != x.end();)
{
k = it;
it++;
if(it==x.end()) {
cout <<"Erasing "<< " [" << (*k).first << ", " << (*k).second << "]" << endl;
x.erase(k);
break;
}

it++;
cout <<"Erasing "<< " [" << (*k).first << ", " << (*k).second << "]" << endl;
x.erase(k);

}

}


This will work....

- kapsi December 01, 2011 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

map<int, int> t;
for (map<int, int>::iterator it = t.begin(); it != t.end(); )
{
t.erase(it++);
if(it == t.end())
break;
it++;
}

- Anonymous January 01, 2012 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

#include <iostream>
#include <algorithm>
#include <set>

int main() {
	std::set<int> myset;	

	for (int i = 0; i < 10; ++i) myset.insert(i*10);	
	std::cout << "before " << std::endl;
	std::for_each(myset.begin(), myset.end(), [](int n) {std::cout << n << std::endl;  });

	std::set<int>::iterator it = myset.begin();
	int n = 0;
	while (it != myset.end()) {
		if (n % 2 == 1) {
			myset.erase(it++);
		}
		else {
			++it;
		}
		n++;
	}

	std::cout << "after " << std::endl;
	std::for_each(myset.begin(), myset.end(), [](int n) {std::cout << n << std::endl;  });

	std::cout << "press enter to continue ..." << std::endl;
	std::cin.get();
	return 0;
}

- Anonymous March 14, 2014 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

We can use

m_map.clear();

- NoIdea December 08, 2016 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

bool must_delete = false;
		
		for (auto it = my.cbegin(); it != my.cend() ; /* no increment */)
		{
			if (must_delete)
			{
				my.erase(it++);    // or "it = m.erase(it)" since C++11
			}
			else
			{
				++it;
			}
			 
			must_delete=!must_delete;
		}

- Siddharth April 08, 2017 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

bool must_delete = false;
		
		for (auto it = my.begin(); it != my.end() /* not hoisted */; /* no increment */)
		{
			if (must_delete)
			{
				my.erase(it++);    // or "it = m.erase(it)" since C++11
			}
			else
			{
				++it;
			}
			 
			must_delete=!must_delete;
		}

- Siddharth April 08, 2017 | Flag Reply


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