cses/introductory.go

package cses

import "fmt"

func WeirdAlgo(n int) string {
	seq := []int{}

	for n != 1 {
		seq = append(seq, n)

		if n%2 == 0 {
			n /= 2
		} else {
			n = n*3 + 1
		}
	}

	seq = append(seq, 1)

	return fmt.Sprint(seq)
}

func MissingNumber(n int, numbers []int) int {

	if n != len(numbers)+1 {
		return -1
	}

	present := make([]bool, n)

	for _, i := range numbers {

		if i > n {
			return -2
		}

		present[i-1] = true
	}

	for i, b := range present {
		if !b {
			return i + 1
		}
	}

	return -3
}

func Repetitions(dna string) int {
	curC := ' '
	maxL := 0
	curL := 0

	for _, c := range dna {
		if c == curC {
			curL += 1
		} else {
			curC = c
			curL = 1
		}

		if curL > maxL {
			maxL = curL
		}
	}

	return maxL
}

func IncreasingArray(size int, arr []int) int {
	moves := 0

	for i := 0; i < len(arr)-1; i++ {
		if arr[i] > arr[i+1] {
			moves += arr[i] - arr[i+1]
		}
	}

	return moves
}

func BeautifulPermutations(n int) string {
	result := []int{}

	if n <= 3 {
		return "NO SOLUTION"
	}

	if n == 4 {
		result = []int{3, 1, 4, 2}
	} else {
		curr := n
		switched := false
		for i := 1; i <= n; i++ {
			result = append(result, curr)
			if curr < 3 && !switched {
				curr = n - 1
				switched = true
			} else {
				curr = curr - 2
			}
		}
	}

	return fmt.Sprint(result)
}

func NumberSpiral(row, col int) int64 {
	result := int64(1)
	var size int

	if row > col {
		size = row
	} else {
		size = col
	}

	for i := 2; i <= size; i++ {
		result = result + int64(2*(i-1))
	}

	switch {
	case col > row:
		if col%2 == 1 {
			result = result + int64(size-row)
		} else {
			result = result + int64(row-size)
		}
	case col < row:
		if row%2 == 1 {
			result = result + int64(col-size)
		} else {
			result = result + int64(size-col)
		}
	}

	return result
}