矩阵旋转分割故障

为hackerrank中的矩阵旋转问题编写代码。我得到分割错误。代码不完整。我已经评论了我认为是制造问题，但不能识别错误的声明。请帮助。

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
struct coord
    {
    int i,j;
    } starting, current;
struct reference
    {
    float i,j;
    } center;
int **a,m,n,t1,t2;    
int goup()
    {
    float dist,dist2;
    dist=sqrt((center.i-current.i)*(center.i-current.i)+(center.j-current.j)*(center.j-current.j));
    do
        {
        t1=a[current.i-1][current.j];
        a[current.i-1][current.j]=t2;//segmentation fault at this statement
        t2=t1;
        current.i--;
        dist=sqrt((center.i-current.i)*(center.i-current.i)+(center.j-current.j)*(center.j-current.j));
        } while(dist2!=dist);
    return 0;
    }
int main()
    {
    int t;
    cin>>m>>n>>t;
    a=new int*[m];
    for(int i=0;i<m;i++)
        a[i]=new int[n];
    for(int i=0;i<m;i++)
        for(int j=0;j<n;j++)
            cin>>a[i][j];
    center.i=(float)(m-1)/2.0;
    center.j=(float)(n-1)/2.0;
    starting.i = center.i + (0.5)*(m%2+1);
    starting.j = center.j + (0.5)*(n%2+1);
    current.i=starting.i;
    current.j=starting.j;
    t2=a[starting.i][starting.j];
    t1=a[starting.i-1][starting.j];
    while(current.i!=m)
        {
        for(int i=0;i<t;i++)
            {
            goup();
            // goleft();
            // godowm();
            // goright();
            }
        starting.i++;
        starting.j++;
        current.i=starting.i;
        current.j=starting.j;
        }
    return 0;
    }