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int IndexOfAny(String[] rgs) would indeed be nice but it's nominally an O(n^2) operation. If, in your application, the set of strings rgs is large and always the same, the most efficient approach is to load them into a <a href="http://en.wikipedia.org/wiki/Trie" rel="nofollow noreferrer">trie</a> data structure once, and then use the trie repeatedly to search for them within the unknown strings given at runtime. Here is the relevant code, adapted from a C# trie source I found on the web, attributed to "Kerry D. Wong." In my version, each string in the trie has a "payload" of generic type TValue. To use this trie to simply search for substrings, the payload could always be set to true, as illustrated with simple_trie. The other thing I changed here is that this trie automatically adapts allow for storage of arbitrary Unicode strings. The array at each node—which characterizes a trie—adjusts its base and length to accomodate the range of Unicode characters which need to be stored at that node. This allows for case-sensitive matching, for example. The C# 3.0 initialization syntax is handy for this trie, but enabling it requires a dummy implementation of IEnumerable in order to compile. The CLR doesn't seem to call GetEnumerator() and I suggest that you don't try to enumerate with its result either. <pre><code>using System; using System.Collections.Generic; using System.Linq; // only used in Main() class Program { // trie with payload of type <String> static Trie<String> value_trie = new Trie<String> { { "rabbit", "cute" }, { "giraffe", "tall" }, { "ape", "smart" }, { "hippo", "large" }, }; // degenerate case of a trie without payload static Trie<bool> simple_trie = new Trie<bool> { { "rabbit", true }, { "giraffe", true }, { "ape", true }, { "hippo", true }, }; static void Main(String[] args) { String s = "Once upon a time, a rabbit met an ape in the woods."; // Retrieve payloads for words in the string. // // output: // cute // smart foreach (String word in value_trie.AllSubstringValues(s)) Console.WriteLine(word); // Simply test a string for any of the words in the trie. // Note that the Any() operator ensures that the input is no longer // traversed once a single result is found. // // output: // True Console.WriteLine(simple_trie.AllSubstringValues(s).Any(e=>e)); s = "Four score and seven years ago."; // output: // False Console.WriteLine(simple_trie.AllSubstringValues(s).Any(e => e)); } } class TrieNode<TValue> { private TrieNode<TValue>[] nodes = null; private TValue m_value = default(TValue); private Char m_base; public Char Base { get { return m_base; } } public bool IsEnd { get { return !m_value.Equals(default(TValue)); } } public TValue Value { get { return m_value; } set { m_value = value; } } public IEnumerable<TrieNode<TValue>> Nodes { get { return nodes; } } public TrieNode<TValue> this[char c] { get { if (nodes != null && m_base <= c && c < m_base + nodes.Length) return nodes[c - m_base]; return null; } } public TrieNode<TValue> AddChild(char c) { if (nodes == null) { m_base = c; nodes = new TrieNode<TValue>[1]; } else if (c >= m_base + nodes.Length) { Array.Resize(ref nodes, c - m_base + 1); } else if (c < m_base) { Char c_new = (Char)(m_base - c); TrieNode<TValue>[] tmp = new TrieNode<TValue>[nodes.Length + c_new]; nodes.CopyTo(tmp, c_new); m_base = c; nodes = tmp; } TrieNode<TValue> node = nodes[c - m_base]; if (node == null) { node = new TrieNode<TValue>(); nodes[c - m_base] = node; } return node; } }; class Trie<TValue> : System.Collections.IEnumerable { private TrieNode<TValue> _root = new TrieNode<TValue>(); // This dummy enables C# 3.0 initialization syntax public System.Collections.IEnumerator GetEnumerator() { return null; } public void Add(String s, TValue v) { TrieNode<TValue> node = _root; foreach (Char c in s) node = node.AddChild(c); node.Value = v; } public bool Contains(String s) { TrieNode<TValue> node = _root; foreach (Char c in s) { node = node[c]; if (node == null) return false; } return node.IsEnd; } public TValue Find(String s_in) { TrieNode<TValue> node = _root; foreach (Char c in s_in) { node = node[c]; if (node == null) return default(TValue); } return node.Value; } public IEnumerable<TValue> FindAll(String s_in) { TrieNode<TValue> node = _root; foreach (Char c in s_in) { node = node[c]; if (node == null) break; if (node.Value != null) yield return node.Value; } } public IEnumerable<TValue> AllSubstringValues(String s) { int i_cur = 0; while (i_cur < s.Length) { TrieNode<TValue> node = _root; int i = i_cur; while (i < s.Length) { node = node[s[i]]; if (node == null) break; if (node.Value != null) yield return node.Value; i++; } i_cur++; } } }; </code></pre>
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1. POEasy way to search a string for strings
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