Create Fancy.ts

Author: masx200

fancy-sequence/Fancy.ts

@@ -0,0 +1,54 @@
+const MOD = 1000000007n;
+export default interface Fancy {
+    getIndex: (idx: number) => number;
+    multAll: (m: number) => void;
+    addAll: (inc: number) => void;
+    append: (val: number) => void;
+}
+
+export default function Fancy(): Fancy {
+    const values: bigint[] = [];
+    let add = 0n;
+    let mult = 1n;
+    let r_mult = 1n;
+
+    const append = function (val: number): void {
+        const result = ((BigInt(val) - add + MOD) * r_mult) % MOD;
+        values.push(result);
+    };
+
+    const addAll = function (inc: number): void {
+        add = (add + BigInt(inc)) % MOD;
+    };
+
+    const multAll = function (m: number): void {
+        const mb = BigInt(m);
+        mult = (mult * mb) % MOD;
+        add = (add * mb) % MOD;
+
+        r_mult = (r_mult * multiplicativeInverse(m, MOD)) % MOD;
+    };
+
+    const getIndex = function (idx: number): number {
+        if (idx >= values.length) return -1;
+        return Number((mult * BigInt(values[idx]) + add) % MOD);
+    };
+    return { getIndex, multAll, addAll, append };
+}
+
+const multiplicativeInverse = function (x: number, mod: bigint): bigint {
+    if (typeof INVERSES[x] !== "undefined") return INVERSES[x];
+    const xb = BigInt(x);
+    const mb = BigInt(mod);
+    let y = 1n,
+        m = mb,
+        p = xb;
+    m = m - 2n;
+
+    for (let i = 0n; 1n << i < m; i++, p = (p * p) % mb)
+        if (((m >> i) & 1n) == 1n) y = (y * p) % mb;
+    INVERSES[x] = y;
+    return y;
+};
+
+const INVERSES: bigint[] = [];