leetcode求栈中最小的元素

55. Min Stack   QuestionEditorial Solution  My Submissions

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.

Example:
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin();   --> Returns -3.
minStack.pop();
minStack.top();      --> Returns 0.

minStack.getMin();   --> Returns -2.

题目的大概意思就是设计一个栈，然后里面可以获得最小的元素，这段代码里面有几个是需要注意的，一个是栈的大小，最小的元素，最小的元素的大小，如何求最小的元素，和求最小的元素的个数，代码：

class MinStack {
private:
   long min=2147483648;
   int min_count=1;
   int *stack;
   int stack_max_count=10000;
   int index=-1;
public:
    /** initialize your data structure here. */
    MinStack() {
        stack=(int *)malloc(sizeof(int)*stack_max_count);
    }
    
    void push(int x) {
        if(x1) min_count--;
                else if(min_count==1){
                    int *tmp_sort=(int*)malloc(sizeof(int)*(index+1));
                    for(int i=0;i<=index;++i){
                        tmp_sort[i]=stack[i];
                    }
                    qsort(tmp_sort,index+1,sizeof(int),comp);
                    min=tmp_sort[0];
                    for(int j=1;j<=index;j++){
                        if(tmp_sort[j]==min) min_count++;
                        else break;
                    }
                }
            }
        }
    int top() {
        return stack[index];
    }
    
    int getMin() {
        return min;
    }
};

/**
 * 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();
 */