fix bigint library wrong behavior

src/bigint_library.cpp

@@ -1,4 +1,4 @@
-/**
+/*
  * Description: BigInt (Big Integer library)
  * Usage: See constructors, operators like +, -, *, /, >, >=, <, <=, ==, toString
  * Note: Remove references '&' in overloaded operators for chaining operations.
@@ -49,7 +49,7 @@ class Bigint {
 
  //Put everything back to original state
  for (int i = 0; i < maxLen; i++) Y[i]=('9'-Y[i])+'0';
-X[lenX]='\0'; Y[lenY]='\0';
+ X[lenX]='\0'; Y[lenY]='\0';
 
  return len;
  }
@@ -83,22 +83,22 @@ class Bigint {
  }
 
  template<class T>
- int divideNmodulo(char *X, int lenX, T divisor, char *Z, T &modulo) {
- int remainder = 0;
- int size = 0;
- for(int i = lenX-1; i >= 0; i--){
- remainder *= 10;
- remainder += X[i]- '0';
- Z[size++] = remainder/divisor + '0';
- remainder %= divisor;
- }
- Z[size]='\0';
- reverse(Z, Z+size);
- modulo = remainder;
- return size;
- }
-
- //Logical Operations
+  int divideNmodulo(char *X, int lenX, T divisor, char *Z, T &modulo) {
+  int remainder = 0;
+  int size = 0;
+  for(int i = lenX-1; i >= 0; i--){
+  remainder *= 10;
+  remainder += X[i]- '0';
+  Z[size++] = remainder/divisor + '0';
+  remainder %= divisor;
+  }
+  Z[size]='\0';
+  reverse(Z, Z+size);
+  modulo = remainder;
+  return size;
+  }
+
+ // Relational Operations
  bool equals(char *X, int lenX, char *Y, int lenY) {
  int maxLen = max(lenX, lenY);
  align(X, maxLen); align(Y, maxLen);
@@ -115,8 +115,9 @@ class Bigint {
  bool greater(char *X, int lenX, char *Y, int lenY) {
  int maxLen = max(lenX, lenY);
  align(X, maxLen); align(Y, maxLen);
- for (int i = maxLen; i >= 0; i--) {
+ for (int i = maxLen - 1; i >= 0; i--) {
  if (X[i] > Y[i]) return true;
+ if (X[i] < Y[i]) return false;
  }
 
  //Put everything back to original state
@@ -181,13 +182,13 @@ class Bigint {
  return modulo;
  }
 
- //Logical Operators
+ // Relational Operators
  bool operator ==(Bigint &b) {
  return equals(this->x, this->length, b.x, b.length);
  }
 
  bool operator >(Bigint &b) {
- return !greater(b.x, b.length, this->x, this->length);
+ return greater(this->x, this->length, b.x, b.length);
  }
 
  bool operator >=(Bigint &b) {
@@ -212,7 +213,10 @@ class Bigint {
  string toString() {
  string s(x, x+length);
  reverse(s.begin(), s.end());
- return trimZeros(s);
+ s = trimZeros(s);
+ if(s.length() == 0)
+ return "0";
+ return s;
  }
 
  friend std::ostream& operator<<(ostream &o, Bigint v) {
@@ -225,10 +229,13 @@ int main() {
  Bigint A("123456789"); // Construct Bigint using string representation
  Bigint B(987654321); // Construct Bigint using integer representation
  Bigint C("456789");
- cout << A * B << endl; // Overridden ostream
- cout << A * B + C << endl; // Chaining operations
- cout << (A > B) << endl;
+ Bigint D("0");
+ cout << "A * B: " << A * B << endl; // Overridden ostream
+ cout << "A * B + C: " << A * B + C << endl; // Chaining operations
+ cout << "(A > B): " << (A > B) << endl;
+ cout << "D: " << D << endl;
  // logical operations
  if (A > B) cout << "A is greater than B" << endl;
- else cout << "B is greater than A" << endl;
+ if (B > A) cout << "B is greater than A" << endl;
+ if (A == B) cout << "A is equal to B" << endl;
 }