30. Substring with Concatenation of All Words

30. Substring with Concatenation of All Words/Solution.cs

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+public class Solution {
+    public IList<int> FindSubstring(string s, string[] words) {
+        var len = words[0].Length;
+        var allLen = len*words.Length;
+        var dict = new Dictionary<string, int>();
+        foreach(var word in words)
+        {
+            dict.TryAdd(word, 0);
+            dict[word]++;
+        }
+        var answer = new List<int>();
+        var dictClone = new Dictionary<string, int>(dict);
+        for(var i = 0; i < s.Length-allLen+1; i++)
+        {
+            var valid = 0;
+            foreach (var kvp in dictClone)
+                dictClone[kvp.Key] = dict[kvp.Key];
+            for(var j=i; j < i+allLen; j+=len)
+            {
+                var word = s[j..(j+len)];
+                if(dictClone.TryGetValue(word, out var count) && count > 0)
+                {
+                    dictClone[word]--;
+                    valid++;
+                }
+                else
+                {
+                    break;
+                }
+            }
+            if(valid == words.Length)
+                answer.Add(i);
+        }
+        return answer;
+    }
+}