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ncr.java
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61 lines (46 loc) · 1.05 KB
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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));
}
}