Triangle

Desicription

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

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[
[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

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class Solution {
public:
int minimumTotal(vector<vector<int>>& triangle) {
for(int i = triangle.size()-2; i >= 0; i--) {
for(int j = 0; j <= i; j++) {
triangle[i][j] += min(triangle[i+1][j], triangle[i+1][j+1]);
}
}
return triangle[0][0];
}
};