resolved #194

Author: ymh199478

src/CatLib.Core.Tests/Support/Util/StrTests.cs

@@ -10,6 +10,7 @@
  */
 
 using System;
+using System.Text;
 using System.Text.RegularExpressions;
 using CatLib.Tests;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
@@ -346,5 +347,25 @@ public void TestIsArr()
             Assert.AreEqual("CatLib.ILRuntime", result[1]);
             Assert.AreEqual("CatLib.Route", result[2]);
         }
+
+        [TestMethod]
+        public void TestLevenshtein()
+        {
+            Assert.AreEqual(4, Str.Levenshtein("hello", "world"));
+            Assert.AreEqual(5, Str.Levenshtein("hello", "catlib"));
+        }
+
+        [TestMethod]
+        public void TestLevenshteinLargeThan255()
+        {
+            var builder = new StringBuilder(256);
+            for (var i = 0; i < 256; i++)
+            {
+                builder.Append('a');
+            }
+
+            Assert.AreEqual(256, builder.Length);
+            Assert.AreEqual(-1, Str.Levenshtein(builder.ToString(), "world"));
+        }
     }
 }

src/CatLib.Core/Support/Util/Str.cs

@@ -491,6 +491,66 @@ public static string Truncate(string str, int length, object separator = null, s
 
             return result + mission;
         }
+
+        /// <summary>
+        /// 计算两个字符串之间的相似度。
+        /// </summary>
+        /// <param name="str1">字符串 1.</param>
+        /// <param name="str2">字符串 2.</param>
+        /// <returns>
+        /// 通过Levenshtein算法返回两个字符串的相似度。如果两个字符串之间的
+        /// 任意一个参数长度大于255那么。将会返回-1。
+        /// </returns>
+        public static int Levenshtein(string str1, string str2)
+        {
+            var length1 = str1.Length;
+            var length2 = str2.Length;
+
+            if (length1 > 255 || length2 > 255)
+            {
+                return -1;
+            }
+
+            var p1 = new int[length2 + 1];
+            var p2 = new int[length1 + 1];
+
+            for (var i = 0; i <= length2; i++)
+            {
+                p1[i] = i;
+            }
+
+            int Min(int num1, int num2, int num3)
+            {
+                var min = num1;
+                if (min > num2)
+                {
+                    min = num2;
+                }
+                if (min > num3)
+                {
+                    min = num3;
+                }
+                return min;
+            }
+
+            for (var i = 0; i < length1; i++)
+            {
+                p2[0] = p1[0] + 1;
+                for (var n = 0; n < length2; n++)
+                {
+                    var distance = str1[i] == str2[n]
+                        ? Min(p1[n], p1[n + 1] + 1, p2[n] + 1)
+                        : Min(p1[n] + 1, p1[n + 1] + 1, p2[n] + 1);
+                    p2[n + 1] = distance;
+                }
+
+                var temp = p1;
+                p1 = p2;
+                p2 = temp;
+            }
+
+            return p1[length2];
+        }
     }
 }