dp_combine.js

// 适用于处理二维数组: ([['a','b'],['c'],['d']],2) --> [[["a","b"],["c"]],[["a","b"],["d"]],[["c"],["d"]]]
function dp_combine(a, m) {
    var t = [[]], r = [];
    for (var i = 0, n = a.length; i < n; ++i) {
        for (var j = 0, l = t.length; j < l; ++j) {
            (t[j].length < m - 1 ? t : r).push(t[j].concat([a[i]]));
        }
    }
    return r;
}