[leetcode]498. Diagonal Traverse

题目链接：https://leetcode.com/problems/diagonal-traverse/?tab=Description

Given a matrix of M x N elements (M rows, N columns), return all elements of the matrix in diagonal order as shown in the below image.

Example:

Input:
[
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
]
Output:  [1,2,4,7,5,3,6,8,9]
Explanation:

class Solution {
public:
vector<int> findDiagonalOrder(vector<vector<int>>& matrix) {
if(matrix.empty())
return vector<int>();
int rowNum=matrix.size();
int colNum=matrix[0].size();
int i=0,j=0;
vector<int> res;
int num=(matrix.size())*matrix[0].size();
int count=0,d=1;
while(count<num)
{
res.push_back(matrix[i][j]);
count+=1;
i-=d;
j+=d;
if(i==rowNum)
{
i=rowNum-1;
j+=2;
d=-d;
}
if(j==colNum)
{
j=colNum-1;
i+=2;
d=-d;
}
if(i<0)
{
i=0;
d=-d;
}
if(j<0)
{
j=0;
d=-d;
}
}
return res;
}
};