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math.go
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math.go
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package math
import (
"strconv"
"strings"
)
/*
* BigNumPlus
* 1.从低位开始相加
* 2.进位重置的时机
* 3.数字串边界问题
*/
func BigNumPlus(n1 string, n2 string) string {
var res string
var carry, u1, u2, sum uint8
var maxLen, idx1, idx2 int
// ascii code:
// +=>43
// -=>45
// 0=>48
// 9=>57
l1 := len(n1)
l2 := len(n2)
if l1 > l2 {
maxLen = l1
} else {
maxLen = l2
}
byteN1 := []byte(n1)
byteN2 := []byte(n2)
for i := 1; i <= maxLen; i++ {
if idx1 = l1 - i; idx1 >= 0 && (byteN1[idx1] >= 48 && byteN1[idx1] <= 57) {
u1 = byteN1[idx1] - 48
}
if idx2 = l2 - i; idx2 >= 0 && (byteN2[idx2] >= 48 && byteN2[idx2] <= 57) {
u2 = byteN2[idx2] - 48
}
sum = u1 + u2 + carry
carry = 0
if sum >= 10 {
carry = 1
sum -= 10
}
res = strconv.Itoa(int(sum)) + res
u1 = 0
u2 = 0
}
return res
}
/*
* BigNumMinus
* @param string n1: It is the bigger one.
* @param string n2: It is the less one.
* 1.从低位开始相加
* 2.进位重置的时机
* 3.借位重置的时机
* 4.数字串边界问题
*/
func BigNumMinus(n1 string, n2 string) string {
var res string
var carry, u1, u2, sum, borrowing uint8
var maxLen, idx1, idx2 int
// ascii code:
// +=>43
// -=>45
// 0=>48
// 9=>57
l1 := len(n1)
l2 := len(n2)
if l1 > l2 {
maxLen = l1
} else {
maxLen = l2
}
byteN1 := []byte(n1)
byteN2 := []byte(n2)
for i := 1; i <= maxLen; i++ {
if idx1 = l1 - i; idx1 >= 0 && (byteN1[idx1] >= 48 && byteN1[idx1] <= 57) {
u1 = byteN1[idx1] - 48
}
if idx2 = l2 - i; idx2 >= 0 && (byteN2[idx2] >= 48 && byteN2[idx2] <= 57) {
u2 = byteN2[idx2] - 48
}
if u1 < u2 {
borrowing = 10
}
sum = u1 - carry - u2 + borrowing
borrowing = 0
carry = 0
if u1 < u2 {
carry = 1
}
res = strconv.Itoa(int(sum)) + res
u1 = 0
u2 = 0
}
res = strings.TrimLeft(res, "0")
if res == "" {
res = "0"
}
return res
}
/*
* BigNumCompare: if n1 is equal or greater than n2, return bool true.
* @param string n1
* @param string n2
*/
func BigNumCompare(n1 string, n2 string) bool {
// ascii code:
// +=>43
// -=>45
// 0=>48
// 9=>57
l1 := len(n1)
l2 := len(n2)
if l1 > l2 {
return true
} else if l1 < l2 {
return false
} else {
byteN1 := []byte(n1)
byteN2 := []byte(n2)
for i := 0; i < l1; i++ {
if byteN1[i] > byteN2[i] {
return true
} else if byteN1[i] < byteN2[i] {
return false
}
}
}
return true
}