LeetCode 118. Pascal’s Triangle

Given numRows, generate the first numRows of Pascal’s triangle.

For example, given numRows = 5,
Return

[
[1],
[1,1],
[1,2,1],
[1,3,3,1],
[1,4,6,4,1]
]

分析：大概是考察用 vector 创建二维数组的应用～

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> v(numRows);
        if(numRows == 0)
            return v;
        for(int i = 0; i < numRows; i++) {
            v[i].resize(i + 1);
        }
        v[0][0] = 1;
        if(numRows == 1)
            return v;
        v[1][0] = 1;
        v[1][1] = 1;
        for(int i = 2; i < numRows; i++) {
            v[i][0] = 1;
            v[i][i] = 1;
        }
        for(int i = 2; i < numRows; i++) {
            for(int j = 1; j < i; j++) {
                v[i][j] = v[i - 1][j - 1] + v[i - 1][j];
            }
        }
        return v;
    }
};

class Solution {

public:

vector<vector<int>> generate(int numRows) {

vector<vector<int>> v(numRows);

if(numRows == 0)

return v;

for(int i = 0; i < numRows; i++) {

v[i].resize(i + 1);

}

v[0][0] = 1;

if(numRows == 1)

return v;

v[1][0] = 1;

v[1][1] = 1;

for(int i = 2; i < numRows; i++) {

v[i][0] = 1;

v[i][i] = 1;

}

for(int i = 2; i < numRows; i++) {

for(int j = 1; j < i; j++) {

v[i][j] = v[i - 1][j - 1] + v[i - 1][j];

}

return v;

}

};