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MinimumPathSum.swift
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MinimumPathSum.swift
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//
// MinimumPathSum.swift
// LeetCode
//
// Created by 黎赵太郎 on 26/11/2017.
// Copyright © 2017 lizhaotailang. All rights reserved.
//
// Given a m x n grid filled with non-negative numbers,
// find a path from top left to bottom right which minimizes the sum of all numbers along its path.
//
// Note: You can only move either down or right at any point in time.
//
// Example 1:
// [[1,3,1],
// [1,5,1],
// [4,2,1]]
// Given the above grid map, return 7. Because the path 1→3→1→1→1 minimizes the sum.
//
// Accepted. See [MinimumPathSumTests](./LeetCodeTests/MinimumPathSumTests.swift) for test cases.
//
import Foundation
class MinimumPathSum {
func minPathSum(_ grid: [[Int]]) -> Int {
if grid.isEmpty {
return 0
}
if grid.count == 1 {
if grid[0].count == 0 {
return 0
}
if grid[0].count == 1 {
return grid[0][0]
}
}
var matrix = Array(repeating: Array(repeating: 0, count: grid[0].count), count: grid.count)
matrix[0][0] = grid[0][0]
var i = 1
while i < grid.count {
matrix[i][0] = matrix[i - 1][0] + grid[i][0]
i += 1
}
i = 1
while i < grid[0].count {
matrix[0][i] = matrix[0][i - 1] + grid[0][i]
i += 1
}
i = 1
while i < grid.count {
var j = 1
while j < grid[0].count {
matrix[i][j] = min(matrix[i - 1][j] + grid[i][j], matrix[i][j - 1] + grid[i][j])
j += 1
}
i += 1
}
// print(matrix)
return matrix[grid.count - 1][grid[0].count - 1]
}
}