Another update from ingydotnet^djgoku

Task/Longest-common-subsequence/JavaScript/longest-common-subsequence-2.js

@@ -1,35 +1,13 @@
-function lcs(x,y){
-	var s,i,j,m,n,
-		lcs=[],row=[],c=[],
-		left,diag,latch;
-	//make sure shorter string is the column string
-	if(m<n){s=x;x=y;y=s;}
-	m = x.length;
-	n = y.length;
-	//build the c-table
-	for(j=0;j<n;row[j++]=0);
-	for(i=0;i<m;i++){
-		c[i] = row = row.slice();
-		for(diag=0,j=0;j<n;j++,diag=latch){
-			latch=row[j];
-			if(x[i] == y[j]){row[j] = diag+1;}
-			else{
-				left = row[j-1]||0;
-				if(left>row[j]){row[j] = left;}
-			}
-		}
-	}
-	i--,j--;
-	//row[j] now contains the length of the lcs
-	//recover the lcs from the table
-	while(i>-1&&j>-1){
-		switch(c[i][j]){
-			default: j--;
-				lcs.unshift(x[i]);
-			case (i&&c[i-1][j]): i--;
-				continue;
-			case (j&&c[i][j-1]): j--;
-		}
-	}
-	return lcs.join('');
-}
+var longest = (xs, ys) => (xs.length > ys.length) ? xs : ys;
+
+var lcs = (xx, yy) => {
+  if (!xx.length || !yy.length) { return ''; }
+
+  var x = xx[0],
+      y = yy[0];
+  xs = xx.slice(1);
+  ys = yy.slice(1);
+
+  return (x === y) ? lcs(xs, ys) :
+                     longest(lcs(xx, ys), lcs(xs, yy));
+};