Long multiplication: Difference between revisions
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→{{header|Sidef}}: added one more implementation
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{{trans|Python}}
<lang ruby>func add_with_carry(result, addend, addendpos) {
while (result.len < addendpos+1) {
result.append(0);
Line 3,733:
say longhand_multiplication('18446744073709551616', '18446744073709551616');</lang>
'''A faster approach:'''
<lang ruby>func long_multiplication(a is String, b is String) -> String {
a.len < b.len && (
[b, a] » (\a, \b);
);
'0' ~~ [a, b] && return '0';
var x = a.split('').map{.to_i}.reverse;
var y = b.split('').map{.to_i}.reverse;
var xlen = x.end;
var ylen = y.end;
var mem = 0;
var map = y.len.of { Array.new };
ylen.range.each { |j|
xlen.range.each { |i|
var n = (x[i]*y[j] + mem);
var(d, m) = n.divmod(10)...;
if (i == xlen) {
map[j].append(m, d);
mem = 0;
}
else {
map[j].append(m);
mem = d;
}
}
var n = (ylen - j);
n > 0 && map[j].append(n.of(0)...);
var m = (ylen - n);
m > 0 && map[j].prepend(m.of(0)...);
}
var result = [];
var mrange = (0 .. map.end);
var end = (xlen + ylen + 1);
end.range.each { |i|
var n = (mrange.map {|j| map[j][i] }.sum + mem);
if (i == end) {
n != 0 && result.append(n);
}
else {
n.divmod(10) » (\mem, \result[result.end+1]);
}
}
result.reverse.join('');
}
say long_multiplication('18446744073709551616', '18446744073709551616');</lang>
{{out}}
<pre>340282366920938463463374607431768211456</pre>
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