About push_back function

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C++

#include <iostream>
#include <string>
#include <vector>
using namespace std;

int main()
{
	vector<char*> coll;
	char str[20];
	for(int i = 0; i < 3; i++)
	{
		cin >> str;
		coll.push_back(str);
	} 
	for(int i = 0; i < 3; i++)
		cout << coll[i]<< endl;
	return 0;
}

When I input 3 strings, why does the vector only catch the last one?
For example when the strings are "China","USA","Russia", the vector only get "Russia".

Posted 7-Dec-12 5:34am

zhangdian

Updated 7-Dec-12 5:47am

v4

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Philippe Mori · Accepted Answer · 2012-12-07T14:17:00

You should use std::string instead of char *.

You always push the same address (str) in the vector and since the vector contains pointers and not values, the values are not copied.

Thus you have added 3 time a pointer to the same address and since the content change at each iteration, at the end, you have the content of the last read string.

Igt is much more simple to use std::string that trying to uses pointers. Thus, you should replace vector<chart *> by vector<string> and your problem will be nicely solved.

Pakh · Accepted Answer · 2012-12-07T05:41:00

Solution 1

The strings are succesfully added in the vector your problem is in printing them
Because you are printing str over and over (3 times) instead of printing coll[i].

Change this

C++

cout << str << endl;

to

C++

cout << coll[i] << endl;

Posted 7-Dec-12 5:41am

Pakh

Updated 7-Dec-12 5:47am

v3

Stephen Hewitt · Accepted Answer · 2012-12-07T05:45:00

Solution 2

for(int i = 0; i < 3; i++)
  cout << coll[i] << endl;

The vector isn't in your output code!

Posted 7-Dec-12 5:45am

Stephen Hewitt

Updated 7-Dec-12 5:46am

v2