9 billion names of God the integer: Difference between revisions

</pre>

Here is faster version

<syntaxhighlight lang="zig">const std = @import("std");

const print = std.debug.print;

const bigint = std.math.big.int.Managed;

const eql = std.mem.eql;

const Array = std.ArrayList;

const Array1 = Array(bigint);

var gpa = std.heap.GeneralPurposeAllocator(.{}){};

const allocator = gpa.allocator();

fn calc ( n:usize, p:*Array1) !void {

for ( 1..n+1 ) |k| {

var d:i64 = @intCast(n);

d -= @intCast(k*(3*k - 1)/2);

inline for ( 0..2 ) |_| {

if ( d < 0 ) return;

if (k&1>0) try p.items[n].add ( &p.items[n], &p.items[@intCast(d)] )

else try p.items[n].sub ( &p.items[n], &p.items[@intCast(d)] );

d -= @intCast(k);

}

}

}

fn main() !void {

const s = [_]usize{ 23, 123, 1234, 12345, 123456 };

var p = Array1.init ( allocator );

try p.append ( try bigint.initSet ( allocator, 1 ) );

var i:usize=1;

for ( s )|m|{

while (i<=m):(i+=1){

try p.append( try bigint.init(allocator) );

try calc( i, &p );

}

print("P({d}) = {d}\n", .{m,p.items[m]} );

}

}

</syntaxhighlight>

{{out}}

<pre>

P(23) = 1255

P(123) = 2552338241

P(1234) = 156978797223733228787865722354959930

P(12345) = 69420357953926116819562977205209384460667673094671463620270321700806074195845953959951425306140971942519870679768681736

P(123456) = 30817659578536496678545317146533980855296613274507139217608776782063054452191537379312358383342446230621170608408020911309259407611257151683372221925128388387168451943800027128045369650890220060901494540459081545445020808726917371699102825508039173543836338081612528477859613355349851184591540231790254269948278726548570660145691076819912972162262902150886818986555127204165221706149989