leetcode_Pascal's Triangle II
2015-05-16 09:29
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描述:
Given an index k, return the kth row of the Pascal's triangle.
For example, given k = 3,
Return
思路:
就是类似杨辉三角的问题,用两个数组存储相邻的两行然后用第一行来算第二行即可,将计算到第k行的数据存储到list中即可。
代码:
public List<Integer> getRow(int rowIndex) {
List<Integer> subList = new ArrayList<Integer>();
int numRows = rowIndex + 1;
if (numRows <= 0)
return subList;
int arr[][] = new int[numRows][];
arr[0] = new int[1];
Arrays.fill(arr[0], 1);
if (numRows > 1) {
arr[1] = new int[2];
Arrays.fill(arr[1], 1);
}
for (int i = 2; i < numRows; i++) {
arr[i] = new int[i + 1];
arr[i][0] = 1;
for (int j = 1; j < i; j++)
arr[i][j] = arr[i - 1][j] + arr[i - 1][j - 1];// to caculate the
// piscal
// triganle
arr[i][i] = 1;
}
for (int num : arr[rowIndex])
subList.add(num);
return subList;
}
Given an index k, return the kth row of the Pascal's triangle.
For example, given k = 3,
Return
[1,3,3,1].
思路:
就是类似杨辉三角的问题,用两个数组存储相邻的两行然后用第一行来算第二行即可,将计算到第k行的数据存储到list中即可。
代码:
public List<Integer> getRow(int rowIndex) {
List<Integer> subList = new ArrayList<Integer>();
int numRows = rowIndex + 1;
if (numRows <= 0)
return subList;
int arr[][] = new int[numRows][];
arr[0] = new int[1];
Arrays.fill(arr[0], 1);
if (numRows > 1) {
arr[1] = new int[2];
Arrays.fill(arr[1], 1);
}
for (int i = 2; i < numRows; i++) {
arr[i] = new int[i + 1];
arr[i][0] = 1;
for (int j = 1; j < i; j++)
arr[i][j] = arr[i - 1][j] + arr[i - 1][j - 1];// to caculate the
// piscal
// triganle
arr[i][i] = 1;
}
for (int num : arr[rowIndex])
subList.add(num);
return subList;
}
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