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msa.go
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msa.go
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package msa
import (
"github.com/catorpilor/leetcode/utils"
)
func maxSubArray(nums []int) int {
return useGreedy(nums)
}
// useGreedy time complexity O(N), space complexity O(1)
func useGreedy(nums []int) int {
if len(nums) < 1 {
return 0
}
sum, maxSofar := nums[0], nums[0]
for i := 1; i < len(nums); i++ {
maxSofar = utils.Max(nums[i], maxSofar+nums[i])
sum = utils.Max(sum, maxSofar)
}
return sum
}
func MaxSubArray2(nums []int) int {
// dp
// dp[j] represents the max sum so far end with jth
// element in nums
// so for dp[i] = dp[i-1] > 0 : dp[i-1] : 0 + nums[i]
// O(n) space and O(n) time
if len(nums) < 1 {
return 0
}
dp := make([]int, len(nums))
dp[0] = nums[0]
maxSofar := nums[0]
for i := 1; i < len(nums); i++ {
dp[i] = nums[i]
if dp[i-1] > 0 {
dp[i] += dp[i-1]
}
maxSofar = utils.Max(maxSofar, dp[i])
}
return maxSofar
}