gistfile1.txt

 const std = @import("std");

const int = i512;
const max_rank: i32 = 1000;
const Map = std.json.ArrayHashMap(int);

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

    var ranks = Map{};
    for (1..@intCast(max_rank + 1)) |i| {
        const buf = try usizeToStr(i, allocator);
        try ranks.map.put(allocator, buf, try formula(@intCast(i), allocator, &ranks));
        std.debug.print("Rank {} : {any}\n", .{ i, ranks.map.get(buf) });
        //allocator.free(buf);
    }

    std.debug.print("Writing file data. Do not stop the program.\n", .{});
    const file = try std.fs.cwd().createFile("ranks.json", .{});
    defer file.close();
    try std.json.stringify(ranks, .{}, file.writer());
    std.debug.print("Done.\n", .{});
}

pub fn usizeToStr(v: usize, alloc: std.mem.Allocator) ![]const u8 {
    return try std.fmt.allocPrint(alloc, "{d}", .{v});
}

pub fn formula(rank: i32, allocator: std.mem.Allocator, ranks: *Map) !int {
    if (rank == 1) {
        const buf = try usizeToStr(1, allocator);
        try ranks.map.put(allocator, buf, formulaBase(rank));
        const value = ranks.map.get(buf).?;
        //allocator.free(value);
        return value;
    }

    const cachedPreviousBuf = try usizeToStr(@as(usize, @intCast(rank)) - 1, allocator);
    const cachedPrevious = ranks.map.get(cachedPreviousBuf).?;
    const buf = try usizeToStr(@as(usize, @intCast(rank)), allocator);
    try ranks.map.put(allocator, buf, cachedPrevious + formulaBase(rank));
    const value = ranks.map.get(buf).?;
    //allocator.free(cachedPrevious);
    return value;
}

pub fn formulaBase(rank: i32) int {
    const rankModed = @as(int, @intCast(rank));
    return 30 * (rankModed * rankModed * rankModed) + 140 * (rankModed * rankModed) + 290 * rankModed + 1180;
}

based