The function ranges(list) takes a sorted array of integers as input [-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20] and returns a string with ranges for the provided input "-6,-3-1,3-5,7-11,14,15,17-20".
A range must consist of three item, i.e. [1, 2] is not considered a range.
A range is formatted as A-B, e.g.: A = -7, B = -1, range is -7--1.
A script by V.
| function ranges(list) { | |
| let output = []; | |
| for (let i = 0, max = list.length; i < max; i++) { | |
| const current = list[i]; | |
| let next = list[i + 1]; | |
| //console.log('current:', current); | |
| if (Math.abs(current - next) !== 1 || !next) { | |
| //console.log('next:', next); | |
| //console.log('push current:', current); | |
| output.push(current); | |
| } else { | |
| let nextNext = list[i + 2]; | |
| loop: | |
| while (next || next === 0) { | |
| //console.log('> select next:', next); | |
| //console.log('> select nextNext:', nextNext); | |
| if (Math.abs(next - nextNext) === 1) { | |
| i++; | |
| next = list[i + 1]; | |
| nextNext = list[i + 2]; | |
| } else { | |
| if (Math.abs(current - next) !== 1) { | |
| const item = current + '-' + next; | |
| //console.log(' >> next > 0, push item:',item); | |
| output.push(item); | |
| } else { | |
| //console.log('push current:',current,' then next:', next); | |
| output.push(current); | |
| output.push(next); | |
| } | |
| i++; | |
| break loop; | |
| } | |
| } | |
| } | |
| } | |
| return output.join(','); | |
| } | |
| // TEST | |
| ranges([-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20]); // returns "-6,-3-1,3-5,7-11,14,15,17-20" |