Create inverse.js

Author: everthis

src/inverse.js

@@ -0,0 +1,13 @@
+function inverse(a, mod) {
+  return quickPow(a, mod - 2, mod) % mod
+}
+
+function quickPow(a, b, p = mod) {
+  let ans = 1;
+  a = (a % p + p) % p;
+  for (; b; b >>= 1) {
+    if (b & 1) ans = (a * ans) % p;
+    a = (a * a) % p;
+  }
+  return ans;
+}