choose

Compute the binomial coefficient, n C k.

example

repl

> var choose = require('choose')
> choose(5,3)
10
> choose(4,4)
1
> choose(7,3)
35

pascal's triangle

var choose = require('choose');
 
var count = Number(process.argv[2]) || 20;
var rows = [];
for (var n = 0; n < count; n++) {
    var row = [];
    for (var k = 0; k <= n; k++) {
        row.push(choose(n, k));
    }
    rows.push(row.join(' '));
}
 
var len = rows[rows.length - 1].length;
rows.forEach(function (row) {
    var n = Math.floor((len - row.length) / 2) + 1;
    console.log(Array(n).join(' ') + row);
});

---

                                               1
                                              1 1
                                             1 2 1
                                            1 3 3 1
                                           1 4 6 4 1
                                         1 5 10 10 5 1
                                       1 6 15 20 15 6 1
                                      1 7 21 35 35 21 7 1
                                    1 8 28 56 70 56 28 8 1
                                  1 9 36 84 126 126 84 36 9 1
                              1 10 45 120 210 252 210 120 45 10 1
                            1 11 55 165 330 462 462 330 165 55 11 1
                          1 12 66 220 495 792 924 792 495 220 66 12 1
                      1 13 78 286 715 1287 1716 1716 1287 715 286 78 13 1
                  1 14 91 364 1001 2002 3003 3432 3003 2002 1001 364 91 14 1
               1 15 105 455 1365 3003 5005 6435 6435 5005 3003 1365 455 105 15 1
           1 16 120 560 1820 4368 8008 11440 12870 11440 8008 4368 1820 560 120 16 1
       1 17 136 680 2380 6188 12376 19448 24310 24310 19448 12376 6188 2380 680 136 17 1
    1 18 153 816 3060 8568 18564 31824 43758 48620 43758 31824 18564 8568 3060 816 153 18 1
1 19 171 969 3876 11628 27132 50388 75582 92378 92378 75582 50388 27132 11628 3876 969 171 19 1

methods

var choose = require('choose')

choose(n, k)

Return the binomial coefficient indexed by the two non-negative integers n and k. That is, return row n, index k of pascal's triangle.

install

With npm do:

npm install choose

license

MIT