main.go

package main

import "fmt"

/*
Take an integer n (n >= 0) and a digit d (0 <= d <= 9) as an integer.

Square all numbers k (0 <= k <= n) between 0 and n.

Count the numbers of digits d used in the writing of all the k**2.

Call nb_dig (or nbDig or ...) the function taking n and d as parameters and returning this count.

Examples:
n = 10, d = 1
the k*k are 0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100
We are using the digit 1 in: 1, 16, 81, 100. The total count is then 4.

nb_dig(25, 1) returns 11 since
the k*k that contain the digit 1 are:
1, 16, 81, 100, 121, 144, 169, 196, 361, 441.
So there are 11 digits 1 for the squares of numbers between 0 and 25.
Note that 121 has twice the digit 1.
*/

func CountExist(number int, squared int) int {
	counter := 0
	numInChar := int32(fmt.Sprint(number)[0])
	for _, char := range fmt.Sprint(squared) {
		if numInChar == char {
			counter++
		}
	}
	return counter
}

func NbDig(n int, d int) int {
	result := 0
	for i := 0; i <= n; i++ {
		result += CountExist(d, i*i)
	}
	return result
}