leetcode day 1

plusone.go

func plusOne(digits []int) []int {
    // access array in reverse order.
    for i := len(digits)-1; i >= 0; i-- {
        if digits[i] != 9 {
            digits[i] = digits[i]+1
            return digits
        } else if i > 0 && digits[i] == 9 {         
            digits[i] = 0
        } else {
            digits[i] = 1
            digits = append(digits, 0) // this particular line helps the array grow when neccessary
        }
    }   
    
    return digits
}

thought-process.md

digits = [9,9,9]
              ^

First Pass: i = 2
   if digits[i] != 9 --> false
   if i(2) > 0 and digits[i] == 9 --> true
        digits[i] = 0
   else <nothing>

digits = [9,9, *0*]

----

[9,9,0]
   ^
Second Pass: i = 1
    if digits[i] != 9 --> false
    if i(1) > 0 and digits[i] == 9 --> true
        digits[i] = 0
    else <nothing> 

digits = [9,*0*,0]

-----

[9,0,0]
 ^
Third Pass: i = 0
    if digits[i] != 9 --> false
    if i(0) > 0 and digits[i] == 9 --> true
    else 
        digits[i] = 1
        digits = append(digits, 0)

digits = [*1*,0,0,*0*]