sub-string-search

for (i = 0, j = 0; i < n && j < m; i++) {
            if (txt.charAt(i) == pat.charAt(j)) j++;
            else {
                i -= j;
                j = 0;
            }
        }
        if (j == m) return i - m;    // found
        else        return n;        // not found

// not a match
for (int i = 0; i <= n - m; i++) {
            int j;
            for (j = 0; j < m; j++) {
                if (txt.charAt(i+j) != pat.charAt(j))
                    break;
            }
            if (j == m) return i;            // found at offset i
        }
        return n;                            // not found