Sync

Task/Modular-inverse/Icon/modular-inverse-1.icon

@@ -0,0 +1,16 @@
+procedure main(args)
+    a := integer(args[1]) | 42
+    b := integer(args[2]) | 2017
+    write(mul_inv(a,b))
+end
+
+procedure mul_inv(a,b)
+    if b == 1 then return 1
+    (b0 := b, x0 := 0, x1 := 1)
+    while a > 1 do {
+        q := a/b
+        (t := b, b := a%b, a := t)
+        (t := x0, x0 := x1-q*x0, x1 := t)
+        }
+    return if (x1 > 0) then x1 else x1+b0
+end

Task/Modular-inverse/Icon/modular-inverse-2.icon

@@ -0,0 +1,19 @@
+link numbers
+
+procedure main(args)
+    a := integer(args[1]) | 42
+    b := integer(args[2]) | 2017
+    write(mul_inv(a,b))
+end
+
+procedure mul_inv(a,b)
+    if b == 1 then return 1
+    if gcd(a,b) ~= 1 then return "not coprime"
+    (b0 := b, x0 := 0, x1 := 1)
+    while a > 1 do {
+        q := a/b
+        (t := b, b := a%b, a := t)
+        (t := x0, x0 := x1-q*x0, x1 := t)
+        }
+    return if (x1 > 0) then x1 else x1+b0
+end

Task/Modular-inverse/PARI-GP/modular-inverse.pari

@@ -0,0 +1 @@
+Mod(1/42,2017)