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MinStack.java
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50 lines (43 loc) · 1015 Bytes
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import java.util.Stack;
/*
* 实现常数时间复杂度实现min栈
* 实现思路：用一个栈来存储数据，用另一个栈来存储当前栈的最小值
*/
public class MinStack {
Stack<Integer> dataStack = new Stack<Integer>();
Stack<Integer> minStack = new Stack<Integer>();
public int min() {
return minStack.peek();
}
public void push(int data) {
if(dataStack.isEmpty()) {
dataStack.push(data);
minStack.push(data);
}
else {
dataStack.push(data);
if(data < minStack.peek()) {
minStack.push(data);
}
else {
minStack.push(minStack.peek());
}
}
}
public Integer pop() {
if(dataStack.isEmpty())
return null;
minStack.pop();
return dataStack.pop();
}
public static void main(String[] args) {
MinStack minStack = new MinStack();
int[] a = {10,9,8,12,1,8,0};
for(int i : a) {
minStack.push(i);
}
while(!minStack.dataStack.isEmpty()) {
System.out.println(minStack.dataStack.pop() + " " + minStack.min());
}
}
}