func maxsubseq(*a) {
    var (start, end, sum, maxsum) = (-1, -1, 0, 0);
    a.each_kv { |i, x|
        sum += x;
        if (maxsum < sum) {
            maxsum = sum;
            end = i;
        }
        elsif (sum < 0) {
            sum = 0;
            start = i;
        }
    };
    a.ft(start+1, end);
}

say maxsubseq(-1, -2,  3,  5,  6, -2, -1,  4, -4,  2, -1);
say maxsubseq(-2, -2, -1,  3,  5,  6, -1,  4, -4,  2, -1);
say maxsubseq(-2, -2, -1, -3, -5, -6, -1, -4, -4, -2, -1);