118.Pascal Triangle

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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.

Example:
Input: 5
Output:
[
[1],
[1,1],
[1,2,1],
[1,3,3,1],
[1,4,6,4,1]
]

我的解法

实现代码

这题比较简单

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class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> ans;
        ans.resize(numRows);
        for (int i = 0; i < numRows; i++){
            ans[i].resize(i + 1);
            for (int j = 0; j < i + 1; j++){
                if (j == 0 || j == i)
                    ans[i][j] = 1;
                else
                    ans[i][j] = ans[i-1][j-1] + ans[i-1][j];
            }
        }
        return ans;
    }
};

Runtime: 4 ms, faster than 60.45% of C++ online submissions for Pascal’s Triangle.
Memory Usage: 8.8 MB, less than 88.89% of C++ online submissions for Pascal’s Triangle.