The problem about the global variable of vector<cv::Mat> and temporary cv::Mat variable

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 #include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>


using namespace std;
using namespace cv;


cv::Mat Right(Size(768,576),CV_8UC3);
cv::Mat Left(Size(768,576),CV_8UC3);

vector<Mat> mapx;
vector<Mat> mapy;


cv::VideoCapture capture1("test.avi");


void MapInit(const Mat &src)
{
    Mat map_x(src.size(),CV_32FC1);
    Mat map_y(src.size(),CV_32FC1);
    for( int i = 0; i < src.rows; ++i)
    {
        for( int j = 0; j < src.cols; ++j)
        {
            map_x.at<float>(i, j) = j ;
            map_y.at<float>(i, j) = src.rows - i ;
        }
    }
    mapx.push_back(map_x);
    mapy.push_back(map_y);
    //Mat map_x1(src.size(),CV_32FC1);
    //Mat map_y1(src.size(),CV_32FC1);
    for( int i = 0; i < src.rows; ++i)
    {
        for( int j = 0; j < src.cols; ++j)
        {
            map_x.at<float>(i, j) = src.cols - j ;
            map_y.at<float>(i, j) =  i ;
            //map_x1.at<float>(i, j) = src.cols - j ;
            //map_y1.at<float>(i, j) =  i ;
        }
    }
    //mapx.push_back(map_x1);
    //mapx.push_back(map_y1);
    mapx.push_back(map_x);
    mapy.push_back(map_y);
}

void mapPlane(const Mat &src)
{
    remap(src,Left,mapx[0],mapy[0],0);
    flip(Left,Left,0);
    remap(src,Right,mapx[1],mapy[1],0);
    //mapx[0] is the same as mapx[1];mapy[0] is the same as mapy[1] ???
    flip(Right,Right,0);
}
void runCam()
{
    namedWindow("test1",0);
    namedWindow("test2",0);
    for(;;)
    {   
        cv::Mat image;
        capture1 >> image;

        if(image.empty())
            exit(0) ;
        cvtColor(image,image,CV_BGR2RGB);
        if(mapx.empty() && mapy.empty())
            MapInit(image);
        mapPlane(image);
        imshow("test1",Left);
        imshow("test2",Right);
        waitKey(20);
    }
}

int main(int argc, char **argv)
{
    if(!capture1.isOpened())
    {
        printf("open failed \n");
        return -1;
    }
    runCam();
    return 0;
}

As above, I create the temporary variable Mat map_x map_y in Function MapInit(),to my surprise, when I pushback the different map_x map_y into vector<mat> mapx,mapy in order,the element of vector<mat> are the same as the latest modified map_x map_y. Similarly, I write a section of code as following,the elements in the vector result are different,which is contradicted against the above example. I am so confused about that.

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

vector<int> result;

void fun()
{
    int i = 0;
    result.push_back(i);
    i = 1;
    result.push_back(i);
}
int main()
{
    fun();
    cout<<result[0]<<endl;
    cout<<result[1]<<endl;
}