1 class Solution {
 2 public:
 3     /**
 4      * @param A, B: Two strings.
 5      * @return: The length of longest common subsequence of A and B.
 6      */
 7     int longestCommonSubsequence(string A, string B) {
 8         // write your code here
 9         int m = A.length(), n = B.length();
10         vector<int> cur(m + 1, 0);
11         for (int j = 1; j <= m; j++) {
12             int pre = 0;
13             for (int i = 1; i <= m; i++) {
14                 int temp = cur[i];
15                 cur[i] = (A[i - 1] == B[j - 1]) ? pre + 1 : max(cur[i], cur[i - 1]);
16                 pre = temp;
17             }
18         }
19         return cur[m];
20     }
21 };