How to insert values in STL map within a loop

Question

I wanted to know how one can insert values in map within a loop. I had used insert() in the following code but this did not worked.

#include<stdio.h>
#include<map>
#include<utility>
using namespace std;
int main()
{
    int t;
    scanf("%d", &t);
    while (t--)
    {
        int n, i;
        map<char*, int> vote;
        char name[20], v;
        scanf("%d", &n);
        for (i = 0; i<n; ++i)
        {
            scanf("%s %c", name, &v);
            vote.insert(make_pair(name, 0));

            vote[name] = 0;
            if (v == '+')
                vote[name]++;
            else
                vote[name]--;
            printf("%d\n", vote[name]);
            printf("Size=%lu\n", vote.size());
        }
        int score = 0;
        for (map<char*, int>::iterator it = vote.begin(); it != vote.end(); ++it)
        {
            printf("%s%d\n", it->first, it->second);
            score += it->second;
        }
        printf("%d\n", score);

    }
}

Everytime I type a new key(string) it just updates the previous one. The size of the map is always 1.

How do I correctly add a new element to the map?

Answer 1

The map is keyed by a pointer (char*). The key in your code is always the same one - the name pointer (Although you change the content that the pointer points on, it does not change the fact that the pointer itself is not the same).

You can use std::string as a key instead of the char*.

Changing the definition of the map (replace char* in std::string) would fix the problem.

EDIT: As @McNabb said, also change it->first to it->first.c_str().