Go语言处理超大字符串型整数加减经典面试详解

fmt.Println(9223372036854775808)

func main(){
    str1 := "314159265358979323846264338327950288419716939937510"
    str2 :=                     "2718281828459045235360287471352"
    rs := ""
    if len(str1) > len(str2) {
        rs = AddStr(str1,str2)
    }  else{
        rs = AddStr(str2,str1)
    }
    fmt.Println(rs)
}
func AddStr(n1,n2 string)(res string) {
    var num []int
    x,y := len(n1),len(n2)
    num = make([]int,x+1) //因为可能存在两个数的最高位相加大于10的情况,故而比两者中最大数的位数+1
    for i :=0;i<y; {
        num[x-i] = int(n1[x-1-i]-'0') + int(n2[y-1-i]-'0')
        i = i + 1
    }
    for i:=0;i<x-y;{
        num[x-y-i] = int(n1[x-y-i-1]-'0')
        i = i + 1
    }
    //处理进位
    for i := len(num);i>1;{
        if num[i-1]/10==1 {
            num[i-1]-=10
            num[i-2]++
        }
        i = i - 1
    }
    //汇总字符串结果
    for _,i := range num{
        s:=strconv.Itoa(i)
        res+=s
    }
    //去除开头可能存在的0
    if len(res) > 1 {
        res = strings.TrimLeft(res,"0")
    }
    return
}

func main(){
    str1 := "314159265358979323846264338327950288419716939937510"
    str2 :=                    "-2718281828459045235360287471352"
    str2 = strings.TrimLeft(str2,"-")
    res := subtractStr(str1,str2)
    fmt.Println(res)
}
func subtractStr(n1,n2 string)(res string) {
  var num []int
  x,y := len(n1),len(n2)
  num= make([]int,x+1)
  for i := 0;i < y; {
      num[x-i] = int(n1[x-1-i]-'0') - int(n2[y-1-i]-'0')
      i = i + 1
  }
  for i:=0;i<x-y;{
      num[x-y-i] = int(n1[x-y-i-1]-'0')
      i = i + 1
  }
  //处理进位
  for i := len(num);i>1;{
      if num[i-1] < 0  {
          num[i-1]+=10
          num[i-2]--
      }
      i = i- 1
  }
  //汇总字符串结果
  for _,i := range num{
      s:=strconv.Itoa(i)
      res+=s
  }
  //去除开头可能存在的0
  if len(res) > 1 {
      res = strings.TrimLeft(res,"0")
  }
  return
}