【LeetCode】232. 用栈实现队列

题目https://leetcode-cn.com/problems/implement-queue-using-stacks/思路用两个栈倒腾让元素的顺序反转两次就回到了原始顺序stackIn是正常栈中顺序stackOut是反转顺序每次push总是往stackIn里加每次pop/peek如果stackOut里面非空那么在stackOut中pop/peek如果stackOut里面为空而且stackIn不为空那么就将stackIn中的全部元素直接push到stackOut中codeclassMyQueue{DequeIntegerstackInnewArrayDeque();DequeIntegerstackOutnewArrayDeque();publicMyQueue(){}publicvoidpush(intx){stackIn.push(x);}publicintpop(){if(empty())return-1;if(!stackOut.isEmpty()){returnstackOut.pop();}else{intcountstackIn.size();for(inti0;icount;i){stackOut.push(stackIn.pop());}returnstackOut.pop();}}publicintpeek(){if(empty())return-1;if(!stackOut.isEmpty()){returnstackOut.peek();}else{intcountstackIn.size();for(inti0;icount;i){stackOut.push(stackIn.pop());}returnstackOut.peek();}}publicbooleanempty(){returnstackIn.isEmpty()stackOut.isEmpty();}}