- 为运算表达式设计优先级
给你一个由数字和运算符组成的字符串 expression ,按不同优先级组合数字和运算符,计算并返回所有可能组合的结果。你可以 按任意顺序 返回答案。
生成的测试用例满足其对应输出值符合 32 位整数范围,不同结果的数量不超过 104 。
示例 1:
输入:expression = "2-1-1"
输出:[0,2]
解释:
((2-1)-1) = 0
(2-(1-1)) = 2
示例 2:
输入:expression = "2*3-4*5"
输出:[-34,-14,-10,-10,10]
解释:
(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
题解:
#include "bits/stdc++.h"
using namespace std;
class Solution {
public:
vector<int> diffWaysToCompute(string expression) {
bool isDigit = true;
vector<int> res;
for (int i = 0; i < expression.size(); ++i) {
if (expression[i] == '+' || expression[i] == '-' || expression[i] == '*') {
isDigit = false;
vector<int> left = diffWaysToCompute(string(expression, 0, i));
vector<int> right = diffWaysToCompute(string(expression, i + 1, expression.size() - i -1));
// 计算左op右的结果
for (auto a : left) {
for (auto b : right) {
if (expression[i] == '+') {
res.push_back(a + b);
} else if (expression[i] == '-') {
res.push_back(a - b);
} else if (expression[i] == '*') {
res.push_back(a * b);
}
}
}
}
}
if (isDigit) {
res.push_back(stoi(expression));
}
return res;
}
};