public static string ToJson(SparseIntVectu32 vector)
{
var sb = new StringBuilder();
sb.Append("{");
sb.Append($"\"size\":{vector.size()},");
sb.Append("\"nonzero\":{");
sb.Append(string.Join(",", vector.GetNonzero().Select(n => $"{n.first}:{n.second}")));
sb.Append("}}");
return sb.ToString();
}
public static int Count(this SparseIntVectu32 v) => (int)v.size();
