leedcode做题总结,题目Evaluate Reverse Polish Notation 2013/11/27
2014-07-21 11:59
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题目:
很简单只需要把数字加入栈里,如果遇到符号了就把前两个数字出栈然后计算后再次入栈即可。
["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9
很简单只需要把数字加入栈里,如果遇到符号了就把前两个数字出栈然后计算后再次入栈即可。
public int evalRPN(String[] tokens) { int leng=tokens.length; Stack<Integer> s = new Stack<Integer>(); for(int i=0;i<leng;i++){ if(tokens[i].equals("+")){ int a=s.pop(); int b=s.pop(); a=a+b; s.push(a); }else if(tokens[i].equals("-")){ int a=s.pop(); int b=s.pop(); a=b-a; s.push(a); }else if(tokens[i].equals("*")){ int a=s.pop(); int b=s.pop(); a=a*b; s.push(a); }else if(tokens[i].equals("/")){ int a=s.pop(); int b=s.pop(); a=b/a; s.push(a); }else{ s.push(Integer.parseInt(tokens[i])); } } return s.pop(); }
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