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Given a non-negative integer numRows , generate the first numRows of Pascal's triangle.
In Pascal's triangle, each number is the sum of the two numbers directly above it.
Example:
Input: 5
Output:
[
[1],
[1,1],
[1,2,1],
[1,3,3,1],
[1,4,6,4,1]
]
杨辉三角是二项式系数的一种写法，如果熟悉杨辉三角的五个性质，那么很好生成，可参见我的上一篇博文Pascal's Triangle II。具体生成算是：每一行的首个和结尾一个数字都是1，从第三行开始，中间的每个数字都是上一行的左右两个数字之和。代码如下：
class Solution {
public:
vector<vector<int>> generate(int numRows) {
vector<vector<int>> res(numRows, vector<int>());
for (int i = 0; i < numRows; ++i) {
res[i].resize(i + 1, 1);
for (int j = 1; j < i; ++j) {
res[i][j] = res[i - 1][j - 1] + res[i - 1][j];
}
}
return res;
}
};
类似题目：
参考资料：
https://leetcode.com/problems/pascals-triangle/
https://leetcode.com/problems/pascals-triangle/discuss/38150/My-C%2B%2B-code-0ms
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