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68 lines
1.7 KiB
Markdown
68 lines
1.7 KiB
Markdown
# [946. Validate Stack Sequences](https://leetcode.com/problems/validate-stack-sequences/)
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## 题目
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Given two sequences pushed and popped with distinct values, return true if and only if this could have been the result of a sequence of push and pop operations on an initially empty stack.
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**Example 1**:
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```
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Input: pushed = [1,2,3,4,5], popped = [4,5,3,2,1]
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Output: true
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Explanation: We might do the following sequence:
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push(1), push(2), push(3), push(4), pop() -> 4,
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push(5), pop() -> 5, pop() -> 3, pop() -> 2, pop() -> 1
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```
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**Example 2**:
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```
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Input: pushed = [1,2,3,4,5], popped = [4,3,5,1,2]
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Output: false
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Explanation: 1 cannot be popped before 2.
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```
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**Note**:
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1. 0 <= pushed.length == popped.length <= 1000
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2. 0 <= pushed[i], popped[i] < 1000
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3. pushed is a permutation of popped.
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4. pushed and popped have distinct values.
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## 题目大意
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给 2 个数组，一个数组里面代表的是 push 的顺序，另一个数组里面代表的是 pop 的顺序。问按照这样的顺序操作以后，最终能否把栈清空？
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## 解题思路
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这一题也是靠栈操作的题目，按照 push 数组的顺序先把压栈，然后再依次在 pop 里面找栈顶元素，找到了就 pop，直到遍历完 pop 数组，最终如果遍历完了 pop 数组，就代表清空了整个栈了。
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## 代码
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```go
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package leetcode
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import "fmt"
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func validateStackSequences(pushed []int, popped []int) bool {
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stack, j, N := []int{}, 0, len(pushed)
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for _, x := range pushed {
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stack = append(stack, x)
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fmt.Printf("stack = %v j = %v\n", stack, j)
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for len(stack) != 0 && j < N && stack[len(stack)-1] == popped[j] {
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stack = stack[0 : len(stack)-1]
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j++
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}
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fmt.Printf("*****stack = %v j = %v\n", stack, j)
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}
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return j == N
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}
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``` |