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摘要： Basic Calculator IIImplement a basic calculator to evaluate a simple expression string.The expression string contains only non-negative integers, +, -... 阅读全文

摘要： Basic CalculatorImplement a basic calculator to evaluate a simple expression string.The expression string may contain open ( and closing parentheses )... 阅读全文

摘要： Integer.MIN_VALUE-1 = Integer.MAX_VALUEInteger.MAX_VALUE+1 = Integer.MIN_VALUE实际上这里是计算机底层的位运算法则问题[1]计算机底层采用了补码来进行加减乘除的运算，好处是符号位参与运算.举上面两个例子来说明问题。Integ... 阅读全文

摘要： Combination Sum IIIFind all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each com... 阅读全文