编辑代码

#include <iostream>
#include <string>
using namespace std;
int getLongestCommonSequence(string wordA, string wordB, string *sequence)
{
    int lengthA = wordA.length();
    int lengthB = wordB.length();
    if (0 == lengthA || 0 == lengthB)
    {
        cout << "Please check word you entered." << endl;
        return -1;
    }
    // 创建表格，横轴是字符串A，纵轴是字符串B
    int **dpArray = new int*[lengthA];
    for (int i = 0; i < lengthA; ++i)
    {
        dpArray[i] = new int[lengthB];
    }
    int maxLength = 0;
    // 填充表格
    for (int i = 0; i < lengthA; ++i)
    {
        for (int j = 0; j < lengthB; ++j)
        {
            // 字符串A的i位置的字符和字符串B的j位置的字符相等
            if (wordA.at(i) == wordB.at(j))
            {
                // 记录下相等的公共子序列长度为1
                dpArray[i][j] = 1;
                // 如果去掉相等的字符后，还有剩余的子串，加上子串的最长公共子序列
                if (i > 0 && j > 0)
                {
                    dpArray[i][j] += dpArray[i - 1][j - 1];
                }
                if (maxLength < dpArray[i][j])
                {
                    sequence->push_back(wordA.at(i));
                    maxLength = dpArray[i][j];
                }
            }
            else
            {
                // 字符串A的i位置的字符和字符串B的j位置的字符不相等
                dpArray[i][j] = 0;
                // 如果去掉字符串A的i位置的字符，字符串A还有子串，记录下剩下的字符串A子串与字符串B的子串的最长公共子序列长度
                if (i > 0) {
                    dpArray[i][j] = dpArray[i - 1][j];
                }

                // 如果去掉字符串B的j位置的字符，字符B还有子串，比较剩下的字符串B子串与字符串A的子串的最长公共子序列长度
                // 与之前去掉字符串A的i位置的字符后的最长公共子序列长度，选取较大的最大公共子序列长度
                if (j > 0 && dpArray[i][j] < dpArray[i][j - 1]) {
                    dpArray[i][j] = dpArray[i][j - 1];
                }
            }
        }    
    }
    // 表格的最后一格就是字符串A和字符串B的最长公共子序列的长度
    maxLength = dpArray[lengthA - 1][lengthB - 1];
    for (size_t i = 0; i < lengthA; i++)
    {
        delete dpArray[i];
    }
    delete [] dpArray;
    return maxLength;
}
int main()
{
    string wordA = "";
    string wordB = "";
    while (true)
    {
        cout << "Please enter word A: " << endl;
        cin >> wordA;
        if (wordA == "0")
        {
            break;
        }
        cout << "Please enter word B: " << endl;
        cin >> wordB;
        string longestCommonSequence = "";
        int length = getLongestCommonSequence(wordA, wordB, &longestCommonSequence);
        cout << "The length of the longest common sequence is " << length << endl;
        cout << longestCommonSequence << endl; 
    } 
}