Triangle
Oct 30 '12
6503 / 17796
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.
class Solution {
public:
int minimumTotal(vector<vector<int> > &triangle) {
int n = triangle.size();
if (n == 0) return 0;
vector<int> res(n);
res[0] = triangle[0][0];
for (int i = 1; i < n; i++) {
res[i] = res[i-1] + triangle[i][i];
for (int j = i - 1; j > 0; j--) {
res[j] = min(res[j-1], res[j]) + triangle[i][j];
}
res[0] += triangle[i][0];
}
int x =res[0];
for (int i = 1; i < n; i++)
if (x > res[i]) x = res[i];
return x;
}
};