[LeetCode] Triangle

Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.

For example, given the following triangle

[
[2],
[3,4],
[6,5,7],
[4,1,8,3]
]

The minimum path sum from top to bottom is

11

(i.e., 2 + 3 + 5 + 1 = 11).

Note:
Bonus point if you are able to do this using only O(n) extra space, where n is the total number of rows in the triangle.

Solution:

class Solution {
public:
int minimumTotal(vector<vector<int> > &triangle) {
int n = triangle.size();
if(n == 0) return 0;

int *sum = new int[n + 1];
sum[0] = triangle[0][0];
for(int i = 1;i < n;i++)
{
sum[i] = sum[i - 1] + triangle[i][i];
for(int j = i - 1;j > 0;j--)
sum[j] = min(sum[j], sum[j - 1]) + triangle[i][j];
sum[0] = sum[0] + triangle[i][0];
}
int minS = 2147483647;
for(int i = 0;i < n;i++)
if(sum[i] < minS)
minS = sum[i];

return minS;
}
};