118.pascals-triangle.cpp

/*
 * @lc app=leetcode id=118 lang=cpp
 *
 * [118] Pascal's Triangle
 *
 * https://leetcode.com/problems/pascals-triangle/description/
 *
 * algorithms
 * Easy (54.23%)
 * Likes:    2267
 * Dislikes: 130
 * Total Accepted:    465.8K
 * Total Submissions: 847.7K
 * Testcase Example:  '5'
 *
 * 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
 * 
 * 
 */

// @lc code=start
class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> result;
        for (int i = 1; i <= numRows; ++i) {
            vector<int> cur(i, 1);
            for (int j = 1; j < i - 1 && i >= 3; ++j) {
                cur[j] = result[i - 2][j - 1] + result[i - 2][j];
            }
            result.push_back(cur);
        }
        return result;
    }
};
// @lc code=end