LeetCode119 Pascal's Triangle II

详细见：leetcode.com/problems/pascals-triangle-ii

Java Solution:
github

package leetcode;

import java.util.ArrayList;
import java.util.List;

/*
* Given an index k, return the kth row of the Pascal's triangle.

For example, given k = 3,
Return [1,3,3,1].

Note:
Could you optimize your algorithm to use only O(k) extra space?
*/

public class P119_PascalsTriangleII {
public static void main(String[] args) {
Solution s = new Solution();
for (int i = -1; i < 11; i ++) {
List<Integer> ans = s.getRow(i);
tools.Utils.B_打印List_Integer_OneLine(ans);
}
}
static class Solution {
public List<Integer> getRow(int rowIndex) {
rowIndex ++;
List<Integer> ans = new ArrayList<>(rowIndex > 0 ? rowIndex : 1);
if (rowIndex <= 1) {
ans.add(1);
return ans;
}
for (int i = 0; i < rowIndex; i ++) {
ans.add(0);
}
ans.set(rowIndex - 1, 1);
ans.set(rowIndex - 2, 1);
int index = rowIndex - 3;
while (index != - 1) {
for (int jndex = index + 1; jndex < rowIndex - 1; jndex ++) {
ans.set(jndex, ans.get(jndex) + ans.get(jndex + 1));
}
ans.set(index, 1);
index --;
}
return ans;
}
}
}


C Solution:
github

/*
url: leetcode.com/problems/pascals-triangle-ii
AC 3ms 2.56%
*/

void swap(int** a, int** b) {
int* t = *a;
*a = *b;
*b = t;
}

int* getRow(int ri, int* rn) {
int* ans = (int*) malloc(sizeof(int) * (ri+1));
int* tmp = (int*) malloc(sizeof(int) * (ri+1));
int i = 0, j = 0, k = 0;
for (i = 0; i <= ri; i ++) {
ans[0] = 1;
for (j = 1; j <= i; j ++) {
ans[j] = tmp[j] + tmp[j-1];
}
ans[i] = 1;
swap(&ans, &tmp);
}
free(ans);
*rn = ri+1;
return tmp;
}

Python Solution:
github

#coding=utf-8

'''
url: leetcode.com/problems/pascals-triangle-ii
@author: zxwtry
@email: zxwtry@qq.com
@date: 2017年5月4日
@details: Solution: 55ms 25.60%
'''

class Solution(object):
def getRow(self, i):
"""
:type i: int
:rtype: List[int]
"""
L, R = [1]*(i+1), [1]*(i+1)
if i < 2: return L
for k in range(2, i):
for j in range(1, k):
R[k][j] = R[k-1][j-1]+R[k-1][j]
L, R = R, L
return L