map undeclared : first use in the function error

Question

#include<stdio.h>
#include<map>

int main()
{
    int cases, i, j, act, answer, min_ind, min_val, temp1, temp2;
    scanf("%d",&cases);

    for(i=0; i<cases; i++)
    {
        answer = 0;
        scanf("%d", &act);
        map<int, int> mymap;

        for(j=0; j<act; j++)
        {
            scanf("%d",&temp1);
            scanf("%d",&temp2);
            mymap[temp2] = temp1;
        }

        map<int,int>::iterator it = mymap.begin();
        temp1 = it->second;

        while(mymap.size() != 0)
        {
            it = mymap.begin();
            if(it->second < temp1)
            {
                mymap.erase(it);
                continue;
            }

            answer++;
            temp1 = it->first;
            mymap.erase(mymap.begin());

            if(mymap.size() != 0)
            {
                it = mymap.begin();
                while(it->second < temp1)
                {
                    mymap.erase(it);
                    it = mymap.begin();
                }
            }
        }

        printf("%d\n",answer);
    }

    return 0;
}

I have included the map header as per the STL of C++ but still its not compiling and giving compilation error. I have tried including map.h header file but still getting the same error

Error:

prog.cpp: In function 'int main()':
prog.cpp:13: error: 'map' was not declared in this scope
prog.cpp:13: error: expected primary-expression before 'int'
prog.cpp:13: error: expected `;' before 'int'
prog.cpp:19: error: 'mymap' was not declared in this scope
prog.cpp:22: error: expected primary-expression before 'int'
prog.cpp:22: error: expected `;' before 'int'

Have a look at my code and help me out with this. Thanks for any help in advance.

It is called writing comments in comments and answers in _answers_. — Lightness Races in Orbit, Jan 01 '14 at 17:45
You can take out the entire body of the main function save the declaration and still get the error. Please do this in the future. See [SSCCE](http://sscce.org). — chris, Jan 01 '14 at 17:45
@chris: [Nobody writes testcases any more](http://kera.name/articles/2013/10/nobody-writes-testcases-any-more/). — Lightness Races in Orbit, Jan 01 '14 at 17:46
@LightnessRacesinOrbit it is a placeholder while I find one of the zillions of duplicates. — juanchopanza, Jan 01 '14 at 17:47
possible duplicate of [C++: 'set' and 'vector' "undeclared despite #include statements](http://stackoverflow.com/questions/9243629/c-set-and-vector-undeclared-despite-include-statements) — juanchopanza, Jan 01 '14 at 17:50
**One question per question.** This isn't a chatroom. Thanks. — Lightness Races in Orbit, Jan 01 '14 at 17:50
@LightnessRacesinOrbit, Well, I did, but I only had time to comment before leaving for a bit. I wholeheartedly agree with the article, though. Very rare is it that I see a test case that is actually a proper one. — chris, Jan 01 '14 at 18:13

user2345215 · Answer 1 · 2014-01-01T17:50:22.600

6

You need to use the std namespace.

Either type std::map instead of map or use using std::map; at the beginning.

Or if you are really lazy, you can type using namespace std; to use all standard functions and types. But beware of name clashes.

edited Jan 01 '14 at 17:50

answered Jan 01 '14 at 17:45

user2345215

637
5
9

Please find the edited part at the end of the question. Would be grateful if I can get any help with that also. – Mcolorz Jan 01 '14 at 17:48
2

@Mcolorz: Don't just randomly tag on a whole new question five minutes later, dude... Post a new one or, better yet, do some research first. – Lightness Races in Orbit Jan 01 '14 at 17:50

score 2 · Answer 2 · answered Jan 01 '14 at 17:44

2

It is in the std namespace, so you need to qualify it: std::map.

answered Jan 01 '14 at 17:44

Joseph Mansfield

108,238
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score 2 · Answer 3 · answered Jan 01 '14 at 17:44

2

It's called std::map. You need to qualify the namespace.

You wouldn't have to do this if you'd written using namespace std; near the top of your program, which I actually don't recommend anyway.

answered Jan 01 '14 at 17:44

Lightness Races in Orbit

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map undeclared : first use in the function error

3 Answers3