Easy C# Solution (Straightforward)
\n    public class Solution\n    {\n        public string SortString(string s)\n        {\n            int[] counts = new int[26];\n            foreach (var c i
```\n    public class Solution\n    {\n        public string SortString(string s)\n        {\n            int[] counts = new int[26];\n            foreach (var c in s)\n            {\n                counts[c - \'a\']++;\n            }\n\n            StringBuilder sb = new StringBuilder(s.Length);\n            int direction = 1;\n            int idx = 0;\n\n            while (sb.Length != s.Length)\n            {\n                if (idx == 26 || idx == -1)\n                {\n                    direction = -direction;\n                    idx += direction;\n                }\n\n                if (counts[idx] > 0)\n                {\n                    counts[idx]--;\n                    sb.Append((char) (idx + \'a\'));\n                }\n\n                idx += direction;\n            }\n\n            return sb.ToString();\n        }\n    }\n```
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