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Copy pathPascalTriangle.java
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40 lines (31 loc) · 1.28 KB
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// Given a non-negative integer numRows, generate the first numRows of Pascal's triangle.
// See: https://leetcode.com/problems/pascals-triangle/
// See: https://leetcode.com/problems/pascals-triangle/discuss/567886/Java-Fast-recursive-solution
package leetcode.others;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
public class PascalTriangle {
public List<List<Integer>> generate(int numRows) {
if (numRows < 2) {
List<List<Integer>> ans = new LinkedList<List<Integer>>();
if (numRows == 1)
ans.add(new LinkedList<>(Arrays.asList(new Integer[] { 1 })));
return ans;
}
List<List<Integer>> res = generate(numRows - 1);
List<Integer> prevRow = res.get(res.size() - 1);
List<Integer> currRow = new LinkedList<>(Arrays.asList(new Integer[] { 1 }));
for (int i = 0; i < prevRow.size() - 1; i++)
currRow.add(prevRow.get(i) + prevRow.get(i + 1));
currRow.add(1);
res.add(currRow);
return res;
}
public static void main(String[] args) {
PascalTriangle sln = new PascalTriangle();
System.out.println(sln.generate(5));
System.out.println(sln.generate(1));
System.out.println(sln.generate(0));
}
}