Solution.java

class Solution {
    private int n;
    private Integer[] f;
    private int[][] g;

    public int deleteString(String s) {
        n = s.length();
        f = new Integer[n];
        g = new int[n + 1][n + 1];
        for (int i = n - 1; i >= 0; --i) {
            for (int j = i + 1; j < n; ++j) {
                if (s.charAt(i) == s.charAt(j)) {
                    g[i][j] = g[i + 1][j + 1] + 1;
                }
            }
        }
        return dfs(0);
    }

    private int dfs(int i) {
        if (i == n) {
            return 0;
        }
        if (f[i] != null) {
            return f[i];
        }
        f[i] = 1;
        for (int j = 1; j <= (n - i) / 2; ++j) {
            if (g[i][i + j] >= j) {
                f[i] = Math.max(f[i], 1 + dfs(i + j));
            }
        }
        return f[i];
    }
}