Comments (7)
kasparsklavins
commented on June 8, 2024
I'll look into it
from bigint.
commented on June 8, 2024
I write this code
#include"bigint.h"
#include<iostream>
using namespace std;
using namespace Dodecahedron;
int main(){
Bigint a,b;
cin>>a>>b;
cout<<a+b<<' '<<a-b;
return 0;
}And this test script ( I believe python's bigint ) in Python3
import subprocess
class Runner:
def __init__(self, args):
self.__process = subprocess.Popen(args, universal_newlines=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
def run(self, input):
self.__output=self.__process.communicate(input)[0]
def get_output(self):
return self.__output
from random import randint
infs = ['1']
for i in range(10000):
infs.append('0')
lo = eval('-'+''.join(infs))
hi = eval(''.join(infs))
while True:
a = randint(lo,hi)
b = randint(lo,hi)
apb = a+b
asb = a-b
inp = str(a)+' '+str(b)
print(inp)
run = Runner("./a")
run.run(inp)
opt = run.get_output()
sta = str(apb) + ' ' + str(asb)
print(opt)
print(sta)
if opt!=sta:
breakThen I found subtraction almost wrong both before #9 and after #9, that means, subtraction is wrong before long, and never ever works.
I tried to fix it. Now it runs perfectly and pass the test script. My fix is at #07ed28b. Here is the core patch for #1b840c7
diff --git a/src/bigint.cpp b/src/bigint.cpp
index 2d47625..8fcc1af 100644
--- a/src/bigint.cpp
+++ b/src/bigint.cpp
@@ -174,20 +174,31 @@ Bigint &Bigint::operator-=(Bigint const &b)
if (it1 != number.end()) {
dif += *it1;
++it1;
+ } else {
+ number.push_back(0);
+ it1 = number.end();
}
if (it2 != b.number.end()) {
dif -= *it2;
++it2;
}
if (dif < 0) {
- *(it1 - 1) = (dif * (-1)) % base;
+ *(it1 - 1) = (dif + base) % base;
dif = -1;
} else {
*(it1 - 1) = dif % base;
dif /= base;
}
}
- if (dif < 0) positive = false;
+ if (dif < 0) {
+ std::string newstr("1");
+ int c_seg = number.size();
+ while(c_seg--)
+ for(int i=1; i<base; i*=10)
+ newstr += "0";
+ *this = Bigint(newstr) - *this;
+ positive = false;
+ }
return *this;
}I worked for long, when right result comes I just feel fly :)
There are 3 main points:
- tell the positive before operation
- push zero back when
ais not large enough - temply use complement number when result is negative, turn back before finish operation
from bigint.
commented on June 8, 2024
Please have a look at my testsuit at branch:test and test on travis ci. As you will see addition & subtraction now run well but multiplication is broken (maybe my changes broke it, I haven't considered leading zero)
from bigint.
commented on June 8, 2024
I had a look at #9 and now I have known what is "leading-zero bug" means, that can be fix for #07ed28b like this
diff --git a/src/bigint.cpp b/src/bigint.cpp
index 8fcc1af..74b0c9a 100644
--- a/src/bigint.cpp
+++ b/src/bigint.cpp
@@ -199,6 +199,8 @@ Bigint &Bigint::operator-=(Bigint const &b)
*this = Bigint(newstr) - *this;
positive = false;
}
+ while (!number.back())
+ number.pop_back();
return *this;
}from bigint.
kasparsklavins
commented on June 8, 2024
Can you do a PR for this?
from bigint.
commented on June 8, 2024
I will try
from bigint.
commented on June 8, 2024
from bigint.
Related Issues (20)
- Error in VS2013 debug enviroment when call "pow" functin HOT 1
- Dead code found at line 78 HOT 3
- Some question about division operation HOT 2
- Bug with big number multiplication HOT 1
- Test coverage HOT 4
- Failed cases HOT 1
- operator* and operator*= HOT 2
- Power of zero HOT 2
- how to (XOR, OR, AND...)? HOT 1
- Incorrect product sign for negative values
- Why doesn't this class support division and modulus? HOT 1
- Performance issue in Bigint::pow function
- if(n==0){//do not work
- I need a modulo operator for this class. Can someone help? Thanks HOT 6
- use bigint with a class
- Not correct string number HOT 3
- Is there a way to get an unsigned version of bigint? HOT 1
- Incorrect initialization with numeric zero
- comparison with 0 cause error HOT 3
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from bigint.