Title
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.
这题以前见过，但忘记哪里见到的了，就是采用两个栈，一个栈保存正常的数据，另一个保存当前栈里面的最小值，只要改下这个push和pop就好了
Solution
//cpp:
class MinStack {
public:
/** initialize your data structure here. */
int min1;
stack<int> a, b;
MinStack() {
min1 = INT_MAX;
}
void push(int x) {
min1 = min(min1, x);
a.push(x);
b.push(min1);
}
void pop() {
a.pop();
b.pop();
if (b.empty())
min1 = INT_MAX;
else
min1 = b.top();
}
int top() {
return a.top();
}
int getMin() {
return b.top();
}
};