pylcs.cpp

// modified from 
// https://github.com/Meteorix/pylcs

#include <string>
#include <vector>
#include <algorithm>
#include "pylcs.hpp"
#include "utf8_unicode.hpp"

using std::string;
using std::vector;

// 最长公共子序列（不连续）
int lcs_length_(const string &str1, const string &str2) {
    if (str1 == "" || str2 == "")
        return 0;
    vector<string> s1 = utf8_split(str1);
    vector<string> s2 = utf8_split(str2);
    int m = s1.size();
    int n = s2.size();
    vector<vector<int>> dp(m + 1, vector<int>(n + 1));
    int i, j;
    // printf("%d %d\n", m, n);

    for (i = 0; i <= m; i++) {
        dp[i][0] = 0;
    }
    for (j = 0; j <= n; j++) {
        dp[0][j] = 0;
    }
    for (i = 1; i <= m; i++) {
        for (j = 1; j <= n; j++) {
            if (s1[i - 1] == s2[j - 1]) {
                dp[i][j] = dp[i - 1][j - 1] + 1;
            } else {
                if (dp[i - 1][j] >= dp[i][j - 1])
                    dp[i][j] = dp[i - 1][j];
                else
                    dp[i][j] = dp[i][j-1];
            }
        }
    }
    return dp[m][n];
}


// 最长公共子串（连续）
// modified by Lorenz Schiffmann, July 2021
// modified to return a struct including also the start position of the lcstr
structRet lcs2_length_(const string &str1, const string &str2) {
    structRet ret;
	ret.max = 0;
	ret.start = 0;	
    if (str1 == "" || str2 == "")
        return ret;
    vector<string> s1 = utf8_split(str1);
    vector<string> s2 = utf8_split(str2);
    int m = s1.size();
    int n = s2.size();
    vector<vector<int>> dp(m + 1, vector<int>(n + 1));
    int i, j;

    for (i = 0; i <= m; i++) {
        dp[i][0] = 0;
    }
    for (j = 0; j <= n; j++) {
        dp[0][j] = 0;
    }
    for (i = 1; i <= m; i++) {
        for (j = 1; j <= n; j++) {
            if (s1[i - 1] == s2[j - 1]) {
                dp[i][j] = dp[i - 1][j - 1] + 1;
                if (dp[i][j] > ret.max){
                    ret.max = dp[i][j];
					ret.start = i-ret.max;
                }
            }
            else {
                dp[i][j] = 0;
            }
        }
    }
    return ret;
}