Leetcode #1143: Longest Common Subsequence

Leetcode_1143.cpp

class Solution {
public:
    int longestCommonSubsequence(string string1, string string2) {
        int n = string1.size();
        int m = string2.size();
        vector<vector<int>> dp(n, vector<int>(m));
        dp[0][0] = string1[0] == string2[0];
        for (int i=1; i<n; i++) {
            dp[i][0] = string1[i] == string2[0] ? 1 : dp[i-1][0];
        }
        for (int j=1; j<m; j++) {
            dp[0][j] = string1[0] == string2[j] ? 1 : dp[0][j-1];
        }
        for (int i=1; i<n; i++) {
            for (int j=1; j<m; j++) {
                dp[i][j] = max({
                                dp[i-1][j],
                                dp[i][j-1],
                                dp[i-1][j-1] + (string1[i]==string2[j])
                               });
            }
        }
        return dp[n-1][m-1];
    }
};
// With clever tricks, the code size can be reduced.
// Also, space complexity can be reduced to O(n) instead of O(n^2).