Data commit

Task/Modular-inverse/Draco/modular-inverse.draco

@@ -0,0 +1,32 @@
+proc mulinv(int a, b) int:
+    int t, nt, r, nr, q, tmp;
+    if b<0 then b := -b fi;
+    if a<0 then a := b - (-a % b) fi;
+    t := 0; nt := 1; r := b; nr := a % b;
+    while nr /= 0 do
+        q := r / nr;
+        tmp := nt; nt := t - q*nt; t := tmp;
+        tmp := nr; nr := r - q*nr; r := tmp
+    od;
+    if r>1 then -1
+    elif t<0 then t+b
+    else t
+    fi
+corp
+
+proc show(int a, b) void:
+    int mi;
+    mi := mulinv(a, b);
+    if mi>=0
+        then writeln(a:5, ", ", b:5, " -> ", mi:5)
+        else writeln(a:5, ", ", b:5, " -> no inverse")
+    fi
+corp
+
+proc main() void:
+    show(42, 2017);
+    show(40, 1);
+    show(52, -217);
+    show(-486, 217);
+    show(40, 2018)
+corp