https://leetcode.com/problems/min-stack/
スタックを実装して、top、pop、push操作を実行できるようにし、同時に現在の最小値を返すこともできる
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入力
-----------------
["MinStack"、 "push"、 "push"、 "push"、 "getMin"、 "pop"、 "top"、 "getMin"]
[[]、[-2]、[0]、[-3] 、[]、[]、[]、[]]
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出力
----------------
[null、null、null、null、-3、null、0、-2]
説明
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3) ;
minStack.getMin(); // -3を
返すminStack.pop();
minStack.top(); // 0を
返すminStack.getMin();// -2を返します
分析:
2つのスタックを設定します。1つは挿入された値を保存し、もう1つは挿入後の現在の要素の最小値を保存します
1.リンクリストを含むスタックを実装する
class MinStack {
public:
/** initialize your data structure here. */
struct StackNode{
int val;
StackNode* next;
StackNode(int val){
this->val = val;
}
};
StackNode* top_stack;
StackNode* min_stack;
MinStack(){
top_stack=NULL;
min_stack=NULL;
}
void push(int x) {
if(!top_stack || x <= min_stack->val)
{
StackNode* temp1 = new StackNode(x);
temp1->next = min_stack;
min_stack = temp1;
}
StackNode* temp = new StackNode(x);
temp->next = top_stack;
top_stack = temp;
}
void pop() {
if(!top_stack)
return;
if(top_stack->val == min_stack->val)
{
StackNode* temp = min_stack;
min_stack = min_stack->next;
delete temp;
}
StackNode* temp1 = top_stack;
top_stack = top_stack->next;
delete temp1;
}
int top() {
return top_stack->val;
}
int getMin() {
return min_stack->val;
}
};
/**
* Your MinStack object will be instantiated and called as such:
* MinStack* obj = new MinStack();
* obj->push(x);
* obj->pop();
* int param_3 = obj->top();
* int param_4 = obj->getMin();
*/
2.組み込みの vector
class MinStack {
public:
/** initialize your data structure here. */
vector<int> top_stack;
vector<int> min_stack;
void push(int x) {
if(top_stack.empty() || x <= min_stack.back())
{
top_stack.push_back(x);
min_stack.push_back(x);
}
else
{
top_stack.push_back(x);
}
}
void pop() {
if(top_stack.back() == min_stack.back())
{
top_stack.pop_back();
min_stack.pop_back();
}
else
top_stack.pop_back();
}
int top() {
return top_stack.back();
}
int getMin() {
return min_stack.back();
}
};
/**
* Your MinStack object will be instantiated and called as such:
* MinStack* obj = new MinStack();
* obj->push(x);
* obj->pop();
* int param_3 = obj->top();
* int param_4 = obj->getMin();
*/