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

October LeetCoding Challenge 1

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
// 44/44 cases passed (35 ms)
// Your runtime beats 20.16 % of cpp submissions
// Your memory usage beats 98.32 % of cpp submissions (6.4 MB)