[HackerRank] The Longest Common Subsequence

This is the classic LCS problem. Since it requires you to print one longest common subsequence, just use the O(m*n)-space version here.

My accepted code is as follows.

 #include <iostream>
 #include <vector>
 #include <algorithm>

 using namespace std;

 vector<int> lcs(vector<int>& a, vector<int>& b) {
     int n = a.size(), m = b.size();
     vector<vector<int> > dp(n + , vector<int> (m + , ));
     for (int i =  ;i <= n; i++) {
         for (int j = ; j <= m; j++) {
             if (a[i - ] == b[j - ]) dp[i][j] = dp[i - ][j - ] + ;
             else dp[i][j] = max(dp[i][j - ], dp[i - ][j]);
         }
     }
     vector<int> res;
     for (int i = n, j = m; i >=  && j >= ;) {
         if (a[i - ] == b[j - ]) {
             res.push_back(a[i - ]);
             i--;
             j--;
         }
         else if (dp[i - ][j] >= dp[i][j - ]) i--;
         else j--;
     }
     reverse(res.begin(), res.end());
     return res;
 }

 int main() {
     /* Enter your code here. Read input from STDIN. Print output to STDOUT */
     int n, m;
     while (scanf("%d %d", &n, &m) != EOF) {
         vector<int> a(n);
         vector<int> b(m);
         for (int i = ; i < n; i++)
             scanf("%d", &a[i]);
         for (int i = ; i < m; i++)
             scanf("%d", &b[i]);
         vector<int> res = lcs(a, b);
         for (int i = ; i < (int)res.size(); i++)
             printf("%d ", res[i]);
         printf("\n");
     }
     return ;
 }

Well, try this problem hereand get Accepted :)