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118.pascals-triangle.cpp
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42 lines (38 loc) · 990 Bytes
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// Tag: Array, Dynamic Programming
// Time: O(N^2)
// Space: O(N)
// Ref: -
// Note: -
// Video: https://youtu.be/gZNCnr7jzJk
// Given an integer numRows, return the first numRows of Pascal's triangle.
// In Pascal's triangle, each number is the sum of the two numbers directly above it as shown:
//
//
// Example 1:
// Input: numRows = 5
// Output: [[1],[1,1],[1,2,1],[1,3,3,1],[1,4,6,4,1]]
// Example 2:
// Input: numRows = 1
// Output: [[1]]
//
//
// Constraints:
//
// 1 <= numRows <= 30
//
//
class Solution {
public:
vector<vector<int>> generate(int numRows) {
vector<vector<int>> res;
for (auto r = 1; r <= numRows; ++r) {
vector<int> ans(r, 1);
for (auto i = 1; i < r - 1; ++i) {
vector<int> previous = res[res.size() - 1];
ans[i] = previous[i - 1] + previous[i];
}
res.push_back(ans);
}
return res;
}
};