int a[]={-2,2,-3,4,-1,2,1,-5,3}; int len=sizeof(a)/sizeof(a[0]);

This code declares an integer array `a` with 9 elements and initializes it with the values -2, 2, -3, 4, -1, 2, 1, -5, and 3.

The variable `len` is then assigned the value of the length of the array `a`, which is determined by dividing the size of the whole array (in bytes) by the size of one element (in bytes). This gives us the number of elements in the array.

Assuming this code is written in C or C++, the types of `a` and `len` are automatically inferred as `int[]` and `int`, respectively.