fib1mil.zig

const std = @import("std");
const Managed = std.math.big.int.Managed;

pub fn main() !void {
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();
    const allocator = gpa.allocator();

    const n = 1_000_000;
    var a = try Managed.initSet(allocator, 0);
    defer a.deinit();
    var b = try Managed.initSet(allocator, 1);
    defer b.deinit();
    var c = try Managed.init(allocator);
    defer c.deinit();

    var i: u32 = 0;
    while (i < n - 1) : (i += 1) {
        try c.add(a.toConst(), b.toConst());
        a.swap(&b);
        b.swap(&c);
    }

    const res = try b.toString(allocator, 10, .lower);
    defer allocator.free(res);
    
    const out = std.io.getStdOut().writer();
    try out.print("fib: {d}\n", .{res.len});
}