1143. Longest Common Subsequence.cpp

Given two strings text1 and text2, return the length of their longest common subsequence.

A subsequence of a string is a new string generated from the original string with some characters(can be none) deleted without changing the relative order of the remaining characters. (eg, "ace" is a subsequence of "abcde" while "aec" is not). A common subsequence of two strings is a subsequence that is common to both strings.



If there is no common subsequence, return 0.



Example 1:

Input: text1 = "abcde", text2 = "ace"
Output: 3
Explanation: The longest common subsequence is "ace" and its length is 3.
Example 2:

Input: text1 = "abc", text2 = "abc"
Output: 3
Explanation: The longest common subsequence is "abc" and its length is 3.
Example 3:

Input: text1 = "abc", text2 = "def"
Output: 0
Explanation: There is no such common subsequence, so the result is 0.


Constraints:

1 <= text1.length <= 1000
1 <= text2.length <= 1000
The input strings consist of lowercase English characters only.






class Solution {
public:

    int LCS(string text1, string text2, int m, int n){
        int dp[m+1][n+1];
        for(int i=0;i<m+1;i++) dp[i][0]=0;
        for(int j=0;j<n+1;j++) dp[0][j]=0;

        for(int i=1;i<m+1;i++){
            for(int j=1;j<n+1;j++){
                if(text1[i-1]==text2[j-1])
                    dp[i][j]=1+dp[i-1][j-1];
                else dp[i][j]=max(dp[i-1][j], dp[i][j-1]);
            }
        }
        return dp[m][n];
    }

    int longestCommonSubsequence(string text1, string text2) {
        int m=text1.length();
        int n=text2.length();

        return LCS(text1, text2, m, n);
    }
};