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Program 1
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The user should construct a new MinStack object within their Java program (no parameters are needed).
They are then free to use the following methods of the MinStack class:
void MinStack.push(int x): Push an integer x onto the stack
int MinStack.pop(): Remove and return the top element of the stack
int MinStack.top(): Return the top element of the stack
int MinStack.getMin(): Return the minimum element of the stack
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Program 2
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The user should input an expression of integers, arithmetic operators (+, -, *, /), and a single equality operator (<, , <=, =, =).
The program will then output whether the expression is true or false.
There should be a space between each integer and symbol. Input in any other format is invalid.
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Program 3
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The user should input an expression in postfix notation. Only single digit values may be used for input.
The program will then output the value of the input expression.
