Interleaving String LeetCode solution in C++

1
/* index shifted by 1 because when memoization applied negative index can't be
2
 * passed as arg for function */
3
class Solution {
4
 public:
5
  bool f(int i, int n, int m, string &s1, string &s2, string &s3, vector<vector<int>> &dp) {
6
    cout << i << n << m << endl;
7
    if (i == 0) return true;
8
    if (n == 0 && m == 0) return false;
9

10
    if (dp[n][m] != -1) return dp[n][m];
11

12
    bool isMatchFoundS1 = false;
13
    if (n > 0 && s1[n - 1] == s3[i - 1]) isMatchFoundS1 = f(i - 1, n - 1, m, s1, s2, s3, dp);
14

15
    bool isMatchFoundS2 = false;
16
    if (m > 0 && s2[m - 1] == s3[i - 1]) isMatchFoundS2 = f(i - 1, n, m - 1, s1, s2, s3, dp);
17

18
    return dp[n][m] = isMatchFoundS1 || isMatchFoundS2;
19
  }
20

21
  bool isInterleave(string s1, string s2, string s3) {
22
    int b = s1.size();
23
    int c = s2.size();
24
    int a = s3.size();
25
    if (b + c != a) return false;
26

27
    vector<vector<int>> dp(b + 1, vector<int>(c + 1, -1));
28

29
    return f(a, b, c, s1, s2, s3, dp);
30
  }
31
};