stringhelper.cs

编译原理语法分析和词法分析综合实验： 源程序、可执行程序、测试程序文件、程序运行说明文件、实验报告。

using System;
using System.Collections.Generic;
using System.Text;

namespace Lane.Compiler.WordAnalyser
{
    public class Distance
    {

        /// <summary>
        /// Compute Levenshtein distance
        /// </summary>
        /// <param name="s">String 1</param>
        /// <param name="t">String 2</param>
        /// <returns>Distance between the two strings.
        /// The larger the number, the bigger the difference.
        /// </returns>
        public static int LD(string s, string t)
        {

            int n = s.Length; //length of s
            int m = t.Length; //length of t
            int[,] d = new int[n + 1, m + 1]; // matrix
            int cost; // cost

            // Step 1
            if (n == 0) return m;
            if (m == 0) return n;

            // Step 2
            for (int i = 0; i <= n; d[i, 0] = i++) ;
            for (int j = 0; j <= m; d[0, j] = j++) ;

            // Step 3
            for (int i = 1; i <= n; i++)
            {

                //Step 4
                for (int j = 1; j <= m; j++)
                {

                    // Step 5
                    cost = (t.Substring(j - 1, 1) == s.Substring(i - 1, 1) ? 0 : 1);

                    // Step 6
                    d[i, j] = System.Math.Min(System.Math.Min(d[i - 1, j] + 1, d[i, j - 1] + 1),
                              d[i - 1, j - 1] + cost);

                }

            }

            // Step 7
            return d[n, m];
        }


    }

}