05 August 2008
设计存储栈内最大值的栈
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class MaxStack {
List<Integer> stack;
int max = Integer.MIN_VALUE;
public MaxStack() {
stack = new ArrayList<>();
}
public void push(int x) {
max = Math.max(x,max);
stack.add(x);
}
public int pop() {
int remove = stack.get(stack.size()-1);
stack.remove(stack.size()-1);
if(remove == max){
getMax();
}
return remove;
}
public int top() {
if(!stack.isEmpty()) {
return stack.get(stack.size()-1);
}
return -1;
}
public int peekMax() {
return max;
}
public int popMax() {
int idx = 0;
for(int i = 0; i < stack.size(); i++) {
if(stack.get(i) == max) idx = i;
}
stack.remove(idx);
int oldMax= max;
getMax();
return oldMax;
}
public void getMax() {
max = Integer.MIN_VALUE;
for(int value : stack) {
max = Math.max(max, value);
}
}
}
/**
* Your MaxStack object will be instantiated and called as such:
* MaxStack obj = new MaxStack();
* obj.push(x);
* int param_2 = obj.pop();
* int param_3 = obj.top();
* int param_4 = obj.peekMax();
* int param_5 = obj.popMax();
*/