1639. Number of ways to form a target string given a dictionary

//1639. Number of ways to form a target string given a dictionary

class Solution {
     static long mod = 1000000007l;

    static public int numWays(String[] words, String targett) {
        int n = words[0].length();
        int m = targett.length();
        long[][] freq = new long[n][26];

        for(int i = 0; i < words.length; i++) {
            for(int j = 0; j < n ; j++) {
                freq[j][words[i].charAt(j) - 'a']++;
            }
        }

        char[] target = targett.toCharArray();
        long[][] dp = new long[n + 1][m + 1];

        for(int i = 0; i <= n; i++) {
            dp[i][0] = 1;
        }

        for(int i = 1; i <= n; i++) {
            for(int j = 1; j <= m; j++) {
                dp[i][j] = dp[i - 1][j];
                dp[i][j] = (dp[i][j] + (freq[i - 1][target[j-1] - 'a'] * dp[i - 1][j - 1])) % mod;
            }
        }

        return (int) dp[n][m];
    }
}