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package DynamicProgramming;

import java.util.Arrays;

public class ncr {

public static int NcR(int n, int r) {

if (n == 1 || r == 0 || n == r) {

return 1;

}

if (r == 1) {

return n;

}

return NcR(n - 1, r) + NcR(n - 1, r - 1);

}

public static int dpApproach(int n, int r) {

if(r > n) return -1;

if(n == r) return 1;

if(r == 0) return n;

int[][] dp = new int[n + 1][r + 1];

for (int i = 1; i <= n; i++) {

for (int j = 0; j <= r; j++) {

if (i >= j) {

if (j == 0) {

dp[i][j] = i;

} else if (i == j) {

dp[i][j] = 1;

} else if (j == 1) {

dp[i][j] = i;

} else {

dp[i][j] = (dp[i - 1][j] + dp[i - 1][j - 1]) % 1000000007;

}

}

}

}

// print(dp);

return dp[n][r];

}

public static void print(int[][] arr) {

for(int i = 0; i < arr.length; i++) {

System.out.println(Arrays.toString(arr[i]));

}

}

public static void main(String[] args) {

// TODO Auto-generated method stub

// System.out.println(NcR(84, 56));

System.out.println(dpApproach(84, 56));

}

}