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website/content/ChapterFour/0946.Validate-Stack-Sequences.md

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+# [946. Validate Stack Sequences](https://leetcode.com/problems/validate-stack-sequences/)
+
+## 题目
+
+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.
+
+ 
+
+**Example 1**:
+
+```
+
+Input: pushed = [1,2,3,4,5], popped = [4,5,3,2,1]
+Output: true
+Explanation: We might do the following sequence:
+push(1), push(2), push(3), push(4), pop() -> 4,
+push(5), pop() -> 5, pop() -> 3, pop() -> 2, pop() -> 1
+
+```
+
+**Example 2**:
+
+```
+
+Input: pushed = [1,2,3,4,5], popped = [4,3,5,1,2]
+Output: false
+Explanation: 1 cannot be popped before 2.
+
+```
+
+**Note**:
+
+1. 0 <= pushed.length == popped.length <= 1000
+2. 0 <= pushed[i], popped[i] < 1000
+3. pushed is a permutation of popped.
+4. pushed and popped have distinct values.
+
+## 题目大意
+
+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？
+
+## 解题思路
+
+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。
+
+## 代码
+
+```go
+
+package leetcode
+
+import "fmt"
+
+func validateStackSequences(pushed []int, popped []int) bool {
+	stack, j, N := []int{}, 0, len(pushed)
+	for _, x := range pushed {
+		stack = append(stack, x)
+		fmt.Printf("stack = %v j = %v\n", stack, j)
+		for len(stack) != 0 && j < N && stack[len(stack)-1] == popped[j] {
+			stack = stack[0 : len(stack)-1]
+			j++
+		}
+		fmt.Printf("*****stack = %v j = %v\n", stack, j)
+	}
+	return j == N
+}
+
+```