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Problem
Given an integer rowIndex, return the rowIndexth row of the Pascal’s triangle.
Notice that the row index starts from 0.
In Pascal’s triangle, each number is the sum of the two numbers directly above it.
Constraints:
- 0 <= rowIndex <= 33
Example1
Input: rowIndex = 3
Output: [1,3,3,1]
Example2
Input: rowIndex = 0
Output: [1]
Example3
Input: rowIndex = 1
Output: [1,1]
Solution
普通DP到滚动数组
class Solution {
public:vector<int> getRow(int n) {vector<vector<int>> f(n+1, vector<int>(n + 1));for (int i = 0; i <= n; i ++ ) {f[i][0] = f[i][i] = 1;for (int j = 1; j < i; j ++ )f[i][j] = f[i - 1 ][j - 1] + f[i - 1][j];}return f[n];}
};
class Solution {
public:vector<int> getRow(int n) {vector<vector<int>> f(2, vector<int>(n + 1));for (int i = 0; i <= n; i ++ ) {f[i & 1][0] = f[i & 1][i] = 1;for (int j = 1; j < i; j ++ )f[i & 1][j] = f[i - 1 & 1][j - 1] + f[i - 1 & 1][j];}return f[n & 1];}
};
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