Min Stack--LeetCode

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Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

push(x) -- Push element x onto stack.
pop() -- Removes the element on top of the stack.
top() -- Get the top element.
getMin() -- Retrieve the minimum element in the stack.

思路：使用向量存储元素，使用一个栈记录当前最小元素的索引，没压栈就是向向量存储元素，同时向栈中压入当前最小元素的索引。

#include <iostream>#include <stack>#include <vector>using namespace std;class Stack{      public:             Stack()             {                    }             ~Stack()             {                     }             int getMin()             {                 int index = minIndex.top();                 return vec[index];             }             void push(int x)             {                  int index = minIndex.top();                  vec.push_back(x);                  if(vec[index] <= x)                    minIndex.push(index);                  else                    minIndex.push(vec.size()-1);                  }             void pop()             {                  vec.pop_back();                  minIndex.pop();                  }             int top()             {                 return vec.back();                 }      private:              vector<int> vec;              stack<int> minIndex;}; int main(){    Stack st;    return 0;    }

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