Pascal’s Triangle
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]]
C++ Solution
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vector<vector<int>> generate(int numRows) {
vector<vector<int>> triangles;
vector<int> lastRow;
for (int i = 0; i < numRows; i++) {
vector<int> row;
if (i == 0) {
row.push_back(1);
}
int curRowNum = i + 1;
int j = 0;
if (!lastRow.empty()) {
while (j < curRowNum - 1) {
int left = 0;
if (j - 1 < 0) {
left = 0;
} else {
left = lastRow[j - 1];
}
row.push_back(lastRow[j] + left);
j++;
}
row.push_back(1);
}
triangles.push_back(row);
lastRow = row;
}
return triangles;
}
