[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; } };