Today I have done leetcode's December LeetCoding Challenge with cpp.

December LeetCoding Challenge 15

Description

Longest Common Subsequence

Given two strings text1 and text2, return the length of their longest common subsequence. If there is no common subsequence, return 0.

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.

• For example, "ace" is a subsequence of "abcde".

A common subsequence of two strings is a subsequence that is common to both strings.

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, text2.length <= 1000
• text1 and text2 consist of only lowercase English characters.

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
  int dp[2][1001] = {};
public:
  int longestCommonSubsequence(string text1, string text2) {
    int len1 = text1.length();
    int len2 = text2.length();
    for(int i = 0; i < len1; ++i) {
      int parity =  i & 1;
      for(int j = 0; j < len2; ++j) {
        dp[parity][j + 1] = max({dp[!parity][j + 1], dp[parity][j], dp[!parity][j] + (text1[i] == text2[j])});
      }
    }
    return dp[~len1 & 1][len2];
  }
};

// Accepted
// 45/45 cases passed (33 ms)
// Your runtime beats 64.49 % of cpp submissions
// Your memory usage beats 98.43 % of cpp submissions (6.3 MB)