Solution to hackerEarth Dexter

DexterAndMandrak.java

package com.algorithms;

/**
 * @Author Mehdi Maick
 * Created on 03/10/2016.
 */

import java.util.*;
import java.io.*;

public class DexterAndMandrak {
    static int t, n, m;
    static int MOD = (int) 1e9 + 7;
    static int[][] memo = new int[1010][1010];

    public static int solve(int curr, int opp) {

        if (memo[curr][opp] != -1) {
            return memo[curr][opp];
        }
        if (curr + opp == n) {
            if (curr > opp) {
                return 1;
            } else {
                return 0;
            }
        }
        int ans = solve(curr + 1, opp) % MOD;
        
        if (curr >= (m * (opp + 1))) {
            ans += solve(curr, opp + 1) % MOD;
        }

        memo[curr][opp] = ans;
        return memo[curr][opp];
    }

    public static void solve(FastReader fs, PrintWriter pw) {
        t = fs.nextInt();
        while (t-- > 0) {
            n = fs.nextInt();
            m = fs.nextInt();
            for (int i = 0; i <= n; i++)
                Arrays.fill(memo[i], -1);
            pw.println(solve(0, 0));
        }
    }

    public static void main(String[] args) throws Exception {
        FastReader fs = new FastReader(System.in);
        PrintWriter pw = new PrintWriter(new OutputStreamWriter(System.out));

        solve(fs, pw);

        fs.close();
        pw.close();
    }

    static class FastReader {

        BufferedReader reader;
        StringTokenizer st;

        FastReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream));
            st = null;
        }

        String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String line = reader.readLine();
                    if (line == null) {
                        return null;
                    }
                    st = new StringTokenizer(line);
                } catch (Exception e) {
                    throw new RuntimeException();
                }
            }
            return st.nextToken();
        }

        String nextLine() {
            String s = null;
            try {
                s = reader.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return s;
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        char nextChar() {
            return next().charAt(0);
        }

        int[] nextIntArray(int n) {
            int[] arr = new int[n];
            int i = 0;
            while (i < n) {
                arr[i++] = nextInt();
            }
            return arr;
        }

        long[] nextLongArray(int n) {
            long[] arr = new long[n];
            int i = 0;
            while (i < n) {
                arr[i++] = nextLong();
            }
            return arr;
        }

        int[] nextIntArrayOneBased(int n) {
            int[] arr = new int[n + 1];
            int i = 1;
            while (i <= n) {
                arr[i++] = nextInt();
            }
            return arr;
        }

        long[] nextLongArrayOneBased(int n) {
            long[] arr = new long[n + 1];
            int i = 1;
            while (i <= n) {
                arr[i++] = nextLong();
            }
            return arr;
        }

        void close() {
            try {
                reader.close();
            } catch (IOException e) {
                System.err.println("There's been an error trying closing the reader ");
                e.printStackTrace();
            }
        }
    }


}