-
-
Save binarymax/1193484 to your computer and use it in GitHub Desktop.
| function( | |
| S, //The Set array | |
| u, //The Subset array to check | |
| b, //Set index | |
| s, //Subset index | |
| e, //Set length | |
| t //Subset length | |
| ) { | |
| var A=S.slice().sort(), //copy and sort set array | |
| B=u.slice().sort(); //copy and sort subset array | |
| b=s=0; //init indexes | |
| e=S.length; //get array lengths | |
| t=u.length; | |
| while(b<e&&s<t) //go until one array hits the end | |
| if(A[b++]==B[s])s++; //if element found from subset in set, inc subset index | |
| return s==t //returns true if every subset element exists | |
| } |
| function(S,u,b,s,e,t){var A=S.slice().sort(),B=u.slice().sort();b=s=0;e=S.length;t=u.length;while(b<e&&s<t)if(A[b++]==B[s])s++;return s==t} |
| DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE | |
| Version 2, December 2004 | |
| Copyright (C) 2011 Max Irwin http://www.binarymax.com/ | |
| Everyone is permitted to copy and distribute verbatim or modified | |
| copies of this license document, and changing it is allowed as long | |
| as the name is changed. | |
| DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE | |
| TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION | |
| 0. You just DO WHAT THE FUCK YOU WANT TO. |
| { | |
| "name": "isSubset", | |
| "description": "Checks if array 'u' is subset of array 'S'.", | |
| "keywords": [ | |
| "subset", | |
| "set" | |
| ] | |
| } |
| <!DOCTYPE html> | |
| <title>Foo</title> | |
| <div>Expected value: <b>true,false,true,true</b></div> | |
| <div>Actual value: <b id="ret"></b></div> | |
| <script> | |
| // write a small example that shows off the API for your example | |
| // and tests it in one fell swoop. | |
| var f = function(S,u,b,s,e,t){var A=S.slice().sort(),B=u.slice().sort();b=s=0;e=S.length;t=u.length;while(b<e&&s<t)if(A[b++]==B[s])s++;return s==t} | |
| var a = ["apples","oranges","bananas","grapes","strawberries"]; | |
| var b = ["strawberries","bananas"]; | |
| var c = ["strawberries","kiwis"]; | |
| var d = []; | |
| var r1 = f(a,b); // b is a subset of a | |
| var r2 = f(a,c); // c is not a subset of a | |
| var r3 = f(a,d); // The empty set is a subset | |
| var r4 = f(a,a); // A set is a subset of itself | |
| document.getElementById( "ret" ).innerHTML = r1 + ',' + r2 + ',' + r3 + ',' + r4; | |
| </script> |
if Array#indexOf is allowed then lets go with a 63 byte one that uses Array#indexOf and Array#every:
function(a,b){return b.every(function(b){return~a.indexOf(b)})}
Nice one, though I'd still prefer it to be alongside a solution that does not require the browser to be ES5-compliant.
Thanks for the info about ES5 Array.indexOf et al.
Btw, you mixed up the two arguments in your 63 bytes implementation. It should read:
function(a,b){return b.every(function(b){return~a.indexOf(b)})}
@p01 yap, I typo'ed and corrected it shortly after (before your comment on it). Reviewing the actual comment instead of the email notification will help prevent mixups like that.
Shortest non ES5-Fallback (tested against Jon's cases):
function(a,b,c,d,e,f){f=0;for(d in b){e=0;for(c in a)e+=a[c]===b[d];f+=e}return!!f}
83bytes, tested in FF6, probable issues with for...in in some engines, yet untested.
Using Array#indexOf or === will fail on a = [NaN], b = [NaN]
Nope, atk's solution (I don't know if it was intentional because his wording makes me think he meant to use String#indexOf) avoids all false positives/negatives presented (even those tests with custom toString() methods). As you pointed out it requires ES5
Array#indexOfor a compliant shim for those enviro's that don't have it.