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jump_game_iii.go
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jump_game_iii.go
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package leetcode
// TC: O(n)
// SC: O(n)
// optimized to not use auxiliary state to track visited nodes
func canReach(arr []int, start int) bool {
if arr[start] == 0 {
return true
}
N := len(arr)
stack := make([][]int, 0)
stack = append(stack, []int{start, arr[start]})
arr[start] = -1
for len(stack) > 0 {
node := stack[len(stack)-1]
stack = stack[:len(stack)-1]
i, d := node[0], node[1]
forward, backward := i+d, i-d
if forward < N && arr[forward] != -1 {
if arr[forward] == 0 {
return true
}
stack = append(stack, []int{forward, arr[forward]})
arr[forward] = -1
}
if backward >= 0 && arr[backward] != -1 {
if arr[backward] == 0 {
return true
}
stack = append(stack, []int{backward, arr[backward]})
arr[backward] = -1
}
}
return false
}
// TC: O(n)
// SC: O(n)
func canReach2(arr []int, start int) bool {
if arr[start] == 0 {
return true
}
N := len(arr)
dp := make([]bool, N)
stack := make([][]int, 0, N)
stack = append(stack, []int{start, arr[start]})
dp[start] = true
for len(stack) > 0 {
node := stack[len(stack)-1]
i, d := node[0], node[1]
stack = stack[:len(stack)-1]
forward, backward := i+d, i-d
if forward < N && dp[forward] == false {
if arr[forward] == 0 {
return true
}
stack = append(stack, []int{forward, arr[forward]})
dp[forward] = true
}
if backward >= 0 && dp[backward] == false {
if arr[backward] == 0 {
return true
}
stack = append(stack, []int{backward, arr[backward]})
dp[backward] = true
}
}
return false
}