标签：push group add example operator toc pos 思想 ret
Given a string of numbers and operators, return all possible results from computing all the different possible ways to group numbers and operators. The valid operators are +, - and *.
Example 1
Input: "2-1-1".
((2-1)-1) = 0 (2-(1-1)) = 2
Output: [0, 2]
Example 2
Input: "2*3-4*5"
(2*(3-(4*5))) = -34 ((2*3)-(4*5)) = -14 ((2*(3-4))*5) = -10 (2*((3-4)*5)) = -10 (((2*3)-4)*5) = 10
Output: [-34, -14, -10, -10, 10]
解题思路：本题的核心思想是 每个运算符都可能是最后运算的操作符。
class Solution { public: int sum=0; int compute(int a,int b,char op){ if(op==‘+‘)return a+b; else if(op==‘-‘)return a-b; else return a*b; } vector<int> diffWaysToCompute(string input) { unordered_map<string,vector<int> >m; return computeWithDp(input,m); } vector<int> computeWithDp(string input,unordered_map<string,vector<int> >&m){ vector<int>res; int size=input.size(); for(int i=0;i<size;i++){ if(input[i]==‘+‘||input[i]==‘-‘||input[i]==‘*‘){ string str=input.substr(0,i); vector<int> l,r; if(m.count(str))return m[str]; else l=diffWaysToCompute(str); str=input.substr(i+1); if(m.count(str))return m[str]; else r=diffWaysToCompute(str); for(auto x: l) for(auto y:r) res.push_back(compute(x,y,input[i])); } } if(res.empty()) res.push_back(stoi(input)); return res; } };
241. Different Ways to Add Parentheses
标签：push group add example operator toc pos 思想 ret
原文地址：http://www.cnblogs.com/tsunami-lj/p/6580942.html
