Category talk:Go-rcu: Difference between revisions
Content added Content deleted
(→Source code: Bug fix.) |
(Improved IsPrime function and genericized the whole package.) |
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import ( |
import ( |
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"fmt" |
"fmt" |
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"golang.org/x/exp/constraints" |
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"math" |
"math" |
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) |
) |
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type Int = constraints.Integer |
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⚫ | |||
⚫ | |||
⚫ | |||
⚫ | |||
if x > y { |
if x > y { |
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return x |
return x |
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} |
} |
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// Returns the smaller of two |
// Returns the smaller of two integers. |
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func Min(x, y |
func Min[T Int](x, y T) T { |
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if x < y { |
if x < y { |
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return x |
return x |
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} |
} |
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// Returns the absolute value of an |
// Returns the absolute value of an integer. |
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func Abs(x |
func Abs[T Int](x T) T { |
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if x < 0 { |
if x < 0 { |
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return -x |
return -x |
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} |
} |
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// Returns the greatest common divisor of two |
// Returns the greatest common divisor of two integers. |
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func Gcd(x, y |
func Gcd[T Int](x, y T) T { |
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for y != 0 { |
for y != 0 { |
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x, y = y, x%y |
x, y = y, x%y |
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} |
} |
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// Returns the least common multiple of two |
// Returns the least common multiple of two integers. |
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func Lcm(x, y |
func Lcm[T Int](x, y T) T { return Abs(x*y) / Gcd(x, y) } |
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// Returns whether or not an |
// Returns whether or not an integer is prime. |
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func IsPrime(n |
func IsPrime[T Int](n T) bool { |
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switch { |
switch { |
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case n < 2: |
case n < 2: |
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case n%3 == 0: |
case n%3 == 0: |
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return n == 3 |
return n == 3 |
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case n%5 == 0: |
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⚫ | |||
default: |
default: |
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d := |
d := T(7) |
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wheel := []T{4, 2, 4, 2, 4, 6, 26} |
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for { |
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for _, w := range wheel { |
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if d*d > n { |
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return true |
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} |
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if n%d == 0 { |
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return false |
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} |
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d += w |
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} |
} |
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⚫ | |||
} |
} |
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return true |
return true |
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Line 71: | Line 78: | ||
// c[i] is false if 'i' is prime or true if 'i' is composite. |
// c[i] is false if 'i' is prime or true if 'i' is composite. |
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// Optionally processes even numbers >= 4. |
// Optionally processes even numbers >= 4. |
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func PrimeSieve(limit |
func PrimeSieve[T Int](limit T, processEven bool) []bool { |
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limit++ |
limit++ |
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// True denotes composite, false denotes prime. |
// True denotes composite, false denotes prime. |
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c[1] = true |
c[1] = true |
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if processEven { |
if processEven { |
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for i := 4; i < limit; i += 2 { |
for i := T(4); i < limit; i += 2 { |
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c[i] = true |
c[i] = true |
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} |
} |
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} |
} |
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p := 3 // Start from 3. |
p := T(3) // Start from 3. |
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for { |
for { |
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p2 := p * p |
p2 := p * p |
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// Returns a slice of all primes up to and including 'limit'. |
// Returns a slice of all primes up to and including 'limit'. |
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func Primes(limit |
func Primes[T Int](limit T) []T { |
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c := PrimeSieve(limit, false) |
c := PrimeSieve(limit, false) |
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if limit < 2 { |
if limit < 2 { |
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return [] |
return []T{} |
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} |
} |
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primes := [] |
primes := []T{2} |
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for i := 3; i < len(c); i += 2 { |
for i := T(3); i < T(len(c)); i += 2 { |
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if !c[i] { |
if !c[i] { |
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primes = append(primes, i) |
primes = append(primes, i) |
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// Sieves for primes up to and including 'n' and returns how many there are. |
// Sieves for primes up to and including 'n' and returns how many there are. |
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// Uses an algorithm better suited to counting than the one used in the PrimeSieve method. |
// Uses an algorithm better suited to counting than the one used in the PrimeSieve method. |
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func PrimeCount(n |
func PrimeCount[T Int](n T) int { |
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if n < 2 { |
if n < 2 { |
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return 0 |
return 0 |
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k := (n-3)/2 + 1 |
k := (n-3)/2 + 1 |
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marked := make([]bool, k) // all false by default |
marked := make([]bool, k) // all false by default |
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limit := ( |
limit := (T(math.Sqrt(float64(n)))-3)/2 + 1 |
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for i := 0; i < limit; i++ { |
for i := T(0); i < limit; i++ { |
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if !marked[i] { |
if !marked[i] { |
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p := 2*i + 3 |
p := 2*i + 3 |
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} |
} |
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} |
} |
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for i := 0; i < k; i++ { |
for i := T(0); i < k; i++ { |
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if !marked[i] { |
if !marked[i] { |
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count++ |
count++ |
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// Returns the prime factors of 'n' in order using a wheel with basis [2, 3, 5]. |
// Returns the prime factors of 'n' in order using a wheel with basis [2, 3, 5]. |
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func PrimeFactors(n |
func PrimeFactors[T Int](n T) []T { |
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if n < 2 { |
if n < 2 { |
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return [] |
return []T{} |
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} |
} |
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inc := [] |
inc := []T{4, 2, 4, 2, 4, 6, 2, 6} |
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var factors [] |
var factors []T |
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for n%2 == 0 { |
for n%2 == 0 { |
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factors = append(factors, 2) |
factors = append(factors, 2) |
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n = n / 5 |
n = n / 5 |
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} |
} |
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for k, i := 7, 0; k*k <= n; { |
for k, i := T(7), 0; k*k <= n; { |
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if n%k == 0 { |
if n%k == 0 { |
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factors = append(factors, k) |
factors = append(factors, k) |
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// Returns all the divisors of 'n' including 1 and 'n' itself. |
// Returns all the divisors of 'n' including 1 and 'n' itself. |
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func Divisors(n |
func Divisors[T Int](n T) []T { |
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if n < 1 { |
if n < 1 { |
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return [] |
return []T{} |
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} |
} |
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var divisors [] |
var divisors []T |
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var divisors2 [] |
var divisors2 []T |
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i := 1 |
i := T(1) |
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k := 1 |
k := T(1) |
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if n%2 == 1 { |
if n%2 == 1 { |
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k = 2 |
k = 2 |
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// Returns all the divisors of 'n' excluding 'n'. |
// Returns all the divisors of 'n' excluding 'n'. |
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func ProperDivisors(n |
func ProperDivisors[T Int](n T) []T { |
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d := Divisors(n) |
d := Divisors(n) |
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c := len(d) |
c := len(d) |
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if c <= 1 { |
if c <= 1 { |
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return [] |
return []T{} |
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} |
} |
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return d[0 : len(d)-1] |
return d[0 : len(d)-1] |
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} |
} |
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// Reverses a slice of |
// Reverses a slice of integers in place. |
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func ReverseInts(s [] |
func ReverseInts[T Int](s []T) { |
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for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 { |
for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 { |
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s[i], s[j] = s[j], s[i] |
s[i], s[j] = s[j], s[i] |
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} |
} |
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// Returns a slice of an |
// Returns a slice of an integer's digits in base b. |
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func Digits(n, b int) []int { |
func Digits[T Int](n T, b int) []int { |
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if n == 0 { |
if n == 0 { |
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return []int{0} |
return []int{0} |
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Line 232: | Line 239: | ||
var digits []int |
var digits []int |
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for n > 0 { |
for n > 0 { |
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digits = append(digits, n%b) |
digits = append(digits, int(n%T(b))) |
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n /= b |
n /= T(b) |
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} |
} |
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ReverseInts(digits) |
ReverseInts(digits) |
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} |
} |
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// Returns the sum of an |
// Returns the sum of an integer's digits in base b. |
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func DigitSum(n, b int) int { |
func DigitSum[T Int](n T, b int) int { |
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sum := 0 |
sum := 0 |
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for n > 0 { |
for n > 0 { |
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sum += n % b |
sum += int(n % T(b)) |
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n /= b |
n /= T(b) |
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} |
} |
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return sum |
return sum |
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} |
} |
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// Returns the sum of a slice of |
// Returns the sum of a slice of integers. |
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func SumInts(a [] |
func SumInts[T Int](a []T) T { |
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sum := 0 |
sum := T(0) |
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for _, i := range a { |
for _, i := range a { |
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sum += i |
sum += i |
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} |
} |
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// Returns the maximum of a slice of |
// Returns the maximum of a slice of integers. |
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func MaxInts(a [] |
func MaxInts[T Int](a []T) T { |
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max := |
max := a[0] |
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for _, i := range a { |
for _, i := range a[1:] { |
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if i > max { |
if i > max { |
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max = i |
max = i |
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} |
} |
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// Returns the minimum of a slice of |
// Returns the minimum of a slice of integers |
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func MinInts(a [] |
func MinInts[T Int](a []T) T { |
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min := |
min := a[0] |
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for _, i := range a { |
for _, i := range a[1:] { |
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if i < min { |
if i < min { |
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min = i |
min = i |
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} |
} |
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// Adds thousand separators to an |
// Adds thousand separators to an integer. |
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func Commatize(n |
func Commatize[T Int](n T) string { |
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s := fmt.Sprintf("%d", n) |
s := fmt.Sprintf("%d", n) |
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if n < 0 { |
if n < 0 { |
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} |
} |
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// Prints a slice of |
// Prints a slice of integers in tabular form with a given row and column size |
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// and optionally comma separators. |
// and optionally comma separators. |
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func PrintTable(s [] |
func PrintTable[T Int](s []T, rowSize, colSize int, commas bool) { |
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for i := 0; i < len(s); i++ { |
for i := 0; i < len(s); i++ { |
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if !commas { |
if !commas { |