LeetCode medium 120. Triangle (Dynamic Programming)
Question:
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.
I always get
fatal error: Can’t form Range with end < start
on “for i in (row-1)…0”.
Thank you so much! Appreciate your time!
class Solution
{
func minimumTotal(triangle: [[Int]]) -> Int
{
if triangle.count == 0
{
return 0
}
if triangle.count == 1
{
return triangle[0][0]
}
var arr = [Int](count: triangle.last!.count, repeatedValue: 0)
let row = triangle.count
for i in (row-1)...0
{
let col = triangle[i].count
for j in 0...col-1
{
if i == row-1
{
arr[i] = triangle[i][j]
continue
}
arr[j] = min(arr[j], arr[j+1]) + triangle[i][j]
}
}
return arr[0]
}
}
var test1 = Solution()
//var input = [[10]]
//var input = [[1],[2,3]]
var input = [[-1],[2,3],[1,-1,-3]]
var result = test1.minimumTotal(input)
print(result)
Answer
for in (0...row-1).reverse()
Swift can’t read row-1…0