int[] arr = {4, 2, 34, 6, 70, 1, -4};

void setup() {
  insertionSort(arr);
  println(arr);
}

void insertionSort(int [] A){
  //insert A[i] in A[0],..A[i] such that A[0]<=A[1]<=...<=A[i]
  for(int i=0; i<A.length; i++){
    int a = A[i];
    int pos = i;
    while((pos>0) && A[pos-1]>=a){
      //move A[pos-1]
      A[pos] = A[pos-1];
      pos--;
    }
    //A[pos] is where a gets inserted
    A[pos] = a;
  }
}