338. Counting Bits

338_counting_bits.go

func countBits(num int) []int {
    results := make([]int, num+1)
    bitsMap := []int{0, 1, 1, 2}
    base := 4

    for i := 0; i < 4; i++ {
        if i > num {
            return results
        }

        results[i] = bitsMap[i]
    }

    bitsMapIndex := 0
    for i := 4; i <= num; i++ {
        if i == base*2 {
            base = base * 2
            bitsMapIndex = 0
        }

        results[i] = 1 + bitsMap[bitsMapIndex]
        bitsMap = append(bitsMap, 1+bitsMap[bitsMapIndex])
        bitsMapIndex++
    }

    return results
}