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Lines changed: 51 additions & 0 deletions

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	`1`	`+package 栈相关.q232_用栈实现队列.f1;`
	`2`	`+`
	`3`	`+import java.util.Stack;`
	`4`	`+`
	`5`	`+/**`
	`6`	`+ * 双栈入队o(n) 出队o(1)`
	`7`	`+ */`
	`8`	`+class MyQueue {`
	`9`	`+`
	`10`	`+ private Stack<Integer> s1 = new Stack<>();`
	`11`	`+ private Stack<Integer> s2 = new Stack<>();`
	`12`	`+ private Integer front;`
	`13`	`+`
	`14`	`+ /** Initialize your data structure here. */`
	`15`	`+ public MyQueue() {`
	`16`	`+`
	`17`	`+ }`
	`18`	`+`
	`19`	`+ /** Push element x to the back of queue. */`
	`20`	`+ public void push(int x) {`
	`21`	`+ if (s1.empty()){`
	`22`	`+ front = x;`
	`23`	`+ }`
	`24`	`+ while (!s1.isEmpty()){`
	`25`	`+ s2.push(s1.pop());`
	`26`	`+ }`
	`27`	`+ s2.push(x);`
	`28`	`+ while (!s2.isEmpty()){`
	`29`	`+ s1.push(s2.pop());`
	`30`	`+ }`
	`31`	`+ }`
	`32`	`+`
	`33`	`+ /** Removes the element from in front of queue and returns that element. */`
	`34`	`+ public int pop() {`
	`35`	`+ int value = s1.pop();`
	`36`	`+ if (!s1.empty()){`
	`37`	`+ front = s1.peek();`
	`38`	`+ }`
	`39`	`+ return value;`
	`40`	`+ }`
	`41`	`+`
	`42`	`+ /** Get the front element. */`
	`43`	`+ public int peek() {`
	`44`	`+ return front;`
	`45`	`+ }`
	`46`	`+`
	`47`	`+ /** Returns whether the queue is empty. */`
	`48`	`+ public boolean empty() {`
	`49`	`+ return s1.isEmpty();`
	`50`	`+ }`
	`51`	`+}`

Lines changed: 49 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,49 @@`
	`1`	`+package 栈相关.q232_用栈实现队列.f2;`
	`2`	`+`
	`3`	`+import java.util.Stack;`
	`4`	`+`
	`5`	`+/**`
	`6`	`+ * 双栈入队o(1) 出队平均o(1),最坏o(n)`
	`7`	`+ */`
	`8`	`+class MyQueue {`
	`9`	`+`
	`10`	`+ private Stack<Integer> s1 = new Stack<>();`
	`11`	`+ private Stack<Integer> s2 = new Stack<>();`
	`12`	`+ private Integer front;`
	`13`	`+`
	`14`	`+ /** Initialize your data structure here. */`
	`15`	`+ public MyQueue() {`
	`16`	`+`
	`17`	`+ }`
	`18`	`+`
	`19`	`+ /** Push element x to the back of queue. */`
	`20`	`+ public void push(int x) {`
	`21`	`+ if (s1.empty()){`
	`22`	`+ front = x;`
	`23`	`+ }`
	`24`	`+ s1.push(x);`
	`25`	`+ }`
	`26`	`+`
	`27`	`+ /** Removes the element from in front of queue and returns that element. */`
	`28`	`+ public int pop() {`
	`29`	`+ if (s2.isEmpty()) {`
	`30`	`+ while (!s1.isEmpty()){`
	`31`	`+ s2.push(s1.pop());`
	`32`	`+ }`
	`33`	`+ }`
	`34`	`+ return s2.pop();`
	`35`	`+ }`
	`36`	`+`
	`37`	`+ /** Get the front element. */`
	`38`	`+ public int peek() {`
	`39`	`+ if (!s2.isEmpty()) {`
	`40`	`+ return s2.peek();`
	`41`	`+ }`
	`42`	`+ return front;`
	`43`	`+ }`
	`44`	`+`
	`45`	`+ /** Returns whether the queue is empty. */`
	`46`	`+ public boolean empty() {`
	`47`	`+ return s1.isEmpty() && s2.isEmpty();`
	`48`	`+ }`
	`49`	`+}`

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