leetcode讲解--946. 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: trueExplanation: 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() -> 1Example 2:Input: pushed = [1,2,3,4,5], popped = [4,3,5,1,2]Output: falseExplanation: 1 cannot be popped before 2.Note:0 <= pushed.length == popped.length <= 10000 <= pushed[i], popped[i] < 1000pushed is a permutation of popped.pushed and popped have distinct values.题目地址讲解典型的栈的题目，练习此题，有助于加深对栈的理解和运用。java代码class Solution { public boolean validateStackSequences(int[] pushed, int[] popped) { Stack<Integer> stack = new Stack<>(); int index=0; for(int i=0;i<popped.length;i++){ if(stack.isEmpty()){ if(index<pushed.length){ stack.push(pushed[index++]); }else{ return false; } } while(popped[i]!=stack.peek()){ if(index<pushed.length){ stack.push(pushed[index++]); }else{ return false; } } stack.pop(); } return true; }}