Here is the question: Given an array of ints, return the number of times that two 6's are next to each other in the array. Also count instances where the second "6" is actually a 7.

Here is the code:

public int array667(int[] nums) {

int len = nums.length;

int count = 0;

for (int i=0;i<len-1;i++){

if ((nums[i]==6) && (nums[i+1]==6||nums[i+1]==7)){

count++;

}

}

return count;

}

I don't understand why it has to be initialized at i-1 in order to work. Please explain

Also are there any other scenarios in which i-1 would be needed maybe even not for just initializing i.