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| // @Title: 为运算表达式设计优先级 (Different Ways to Add Parentheses)
// @Author: 15816537946@163.com
// @Date: 2019-11-18 17:48:43
// @Runtime: 0 ms
// @Memory: 2.1 MB
func diffWaysToCompute(input string) []int {
cache := make(map[string][]int)
var dfs func(string) []int
dfs = func(s string) []int {
res := make([]int, 0, len(s))
if t, ok := cache[s]; ok {
return t
}
for i := range s {
if s[i] == '+' || s[i] == '-' || s[i] == '*' {
// 此时,s[i] 作为最后一个运算的运算符
for _, left := range dfs(s[:i]) {
for _, right := range dfs(s[i+1:]) {
res = append(res, operate(left, right, s[i]))
}
}
}
}
// s 中不存在运算符
if len(res) == 0 {
temp, _ := strconv.Atoi(s)
res = append(res, temp)
}
cache[s] = res
return res
}
return dfs(input)
}
func operate(a, b int, opt byte) int {
switch opt {
case '+':
return a + b
case '-':
return a - b
default:
return a * b
}
}
|