Implement FreqStack, a class which simulates the operation of a stack-like data structure.
FreqStack`has two functions:
- push(int x), which pushes an integer x onto the stack.
- pop(), which removes and returns the most frequent element in the stack.
- If there is a tie for most frequent element, the element closest to the top of the stack is removed and returned.
Example 1:
Input:
["FreqStack","push","push","push","push","push","push","pop","pop","pop","pop"],
[[],[5],[7],[5],[7],[4],[5],[],[],[],[]]
Output: [null,null,null,null,null,null,null,5,7,5,4]
Explanation:
After making six .push operations, the stack is [5,7,5,7,4,5] from bottom to top. Then:
pop() -> returns 5, as 5 is the most frequent.
The stack becomes [5,7,5,7,4].
pop() -> returns 7, as 5 and 7 is the most frequent, but 7 is closest to the top.
The stack becomes [5,7,5,4].
pop() -> returns 5.
The stack becomes [5,7,4].
pop() -> returns 4.
The stack becomes [5,7].
Note:
- Calls to FreqStack.push(int x)`will be such that 0 <= x <= 10^9.
- It is guaranteed that FreqStack.pop() won't be called if the stack has zero elements.
- The total number of FreqStack.push calls will not exceed 10000 in a single test case.
- The total number of FreqStack.pop`calls will not exceed 10000 in a single test case.
- The total number of FreqStack.push and FreqStack.pop calls will not exceed 150000 across all test cases.
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