Data commit

Task/Range-extraction/JavaScript/range-extraction-4.js

@@ -0,0 +1,50 @@
+function toRange(arr) {
+    const ranges = [];
+    const sorted = [...arr.filter(Number.isInteger)].sort((x,y) => Math.sign(x-y));
+    const sequenceBreak = (x,y) => y - x > 1 ;
+
+    let i = 0;
+    while ( i < sorted.length ) {
+
+        let j = i ;
+        while ( j < sorted.length - 1 && !sequenceBreak( sorted[j], sorted[j+1] ) ) {
+            ++j;
+        }
+
+        const from = sorted[i];
+        const thru = sorted[j];
+        const rangeLen = 1 + j - i;
+
+        if ( from === thru ) {
+            ranges.push( [from] );
+        } else {
+            if ( rangeLen > 2 ) {
+                ranges.push([from,thru]);
+            } else {
+                ranges.push([from], [thru]);
+            }
+        }
+
+        i = j+1;
+    }
+
+    return ranges.map( range => range.join('-') ).join(',');
+}
+
+// -----------------------------------------------------------------------------
+// Test Case
+// -----------------------------------------------------------------------------
+const expected = '0-2,4,6-8,11,12,14-25,27-33,35-39';
+const actual = toRange([
+     0,  1,  2,
+     4,
+     6,  7,  8,
+    11, 12, // should be two singletons
+    14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
+    27, 28, 29, 30, 31, 32, 33,
+    35, 36, 37, 38, 39,
+]);
+
+console.log(`actual output   : '${actual}'.`);
+console.log(`expected output : '${expected}'.`);
+console.log(`Correct? ${ actual === expected ? 'Yes' : 'No'}`);