Longest Common Subsequence

https://leetcode.com/problems/longest-common-subsequence/

Description

longest common subsequence

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.

Solution Dynamic programming

class Solution {
public:
    int longestCommonSubsequence(string text1, string text2) {
        int m = text1.size();
        int n = text2.size();
        int i,j;
        int dp[m+1][n+1];
        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(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];
    }
};