careercup 16.10

Write a function called my2DAlloc which allocates a two dimensional array. Minimize the number of calls to malloc and make sure that the memory is accessible by the notation arr[i][j].

假设要申请N*M的内存

arr = malloc(sizeof(int*)*N);
arr[0]=malloc(sizeof(int*)*N*M)
for(int i=1;i<N;i++) arr[i]=arr[i-1]+M;