import java.util.Stack;
public class GetMinStack {
private Stack<Integer> stackData;
private Stack<Integer> stackMin;
public GetMinStack() {
stackData = new Stack<>();
stackMin = new Stack<>();
}
public Integer pop() {
if (stackData.isEmpty()) {
throw new RuntimeException("Stack is Empty!");
}
int val = stackData.pop();
if (val == getMin()) {
stackMin.pop();
}
return val;
}
public void push(Integer val) {
if (stackMin.isEmpty()) {
stackMin.push(val);
} else if(val <= getMin()){
stackMin.push(val);
}
stackData.push(val);
}
public Integer getMin() {
if (stackMin.isEmpty()) {
throw new RuntimeException("Stack is Empty!");
}
return stackMin.peek();
}
}
解法2
import java.util.Stack;
public class GetMinStack2 {
private Stack<Integer> stackData;
private Stack<Integer> stackMin;
public GetMinStack2() {
stackData = new Stack<>();
stackMin = new Stack<>();
}
public Integer pop() {
if (stackData.isEmpty()) {
throw new RuntimeException("Stack is Empty!");
}
stackMin.pop();
return stackData.pop();
}
public void push(Integer val) {
if (stackMin.isEmpty()) {
stackMin.push(val);
} else if(val <= getMin()){
stackMin.push(val);
} else {
int min = stackMin.peek();
stackMin.push(min);
}
stackData.push(val);
}
public Integer getMin() {
if (stackMin.isEmpty()) {
throw new RuntimeException("Stack is Empty!");
}
return stackMin.peek();
}
}
