题目描述
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.
Example1:
Input: 5 Output: [ [1], [1,1], [1,2,1], [1,3,3,1], [1,4,6,4,1] ]
class Solution {
public:
vector<vector<int>> generate(int numRows) {
vector<vector<int>> res;
for(int i = 1; i <= numRows; i++){ // 注意下标问题 i从1开始
vector<int> t(i, 1);
for(int j = 1; j < i - 1; j++){
t[j] = res[i - 2][j - 1] + res[i - 2][j]; // 第一行赋值的应该是i-2
}
res.push_back(t);
}
return res;
}
};
