Feat: Multiply Operator (*) overload with tests

big-int/src/operators/multiply.cpp

@@ -35,17 +35,38 @@ namespace libbig
 {
     largeInt largeInt::operator*(const largeInt &next_number) {
 
-        auto append_zeroes = [](const largeInt &x, const int factor) {
-            int k;
+        using Iterator = std::string::reverse_iterator; 
+
+        auto remove_zeroes = [] (const largeInt &x) {
             largeInt Answer = x;
-            for(k = 0; k < factor; k++) {
+            std::reverse(Answer.number.begin(), Answer.number.end());
+            for(Iterator j=Answer.number.rbegin(); j != Answer.number.rend() - 1; ++j) {
+                if((*j) == '0') {
+                    Answer.number.pop_back();
+                }
+                else {
+                    break;
+                }
+            }
+            std::reverse(Answer.number.begin(), Answer.number.end());
+            return Answer;
+        };
+
+        auto append_zeroes = [] (const largeInt &x, const int factor) {
+            largeInt Answer = x;
+            for(int k = 0; k < factor; k++) {
                 Answer.number.push_back('0');
             }
 
             return Answer;
         };
 
-        auto simple_multiplication = [](const largeInt &x, const largeInt &y) {
+        auto simple_multiplication = [] (const largeInt &x, const largeInt &y) {
+
+            auto char_int_converter = [] (const char &x) {
+                return ((x >= '0' && x <= '9') ? x - '0' : x + '0') ;
+            };
+
             largeInt x1 = x;
             largeInt x2 = y;
             largeInt adder;
@@ -55,27 +76,24 @@ namespace libbig
                 return largeInt();
             }
 
-            int carry { 0 }, temp, f=1, k;
-            std::string::reverse_iterator i, j;
-            for(i=x1.number.rbegin(); i!=x1.number.rend(); ++i) {
-                for(j=x2.number.rbegin(); j!=x2.number.rend(); ++j) {
-                    temp = (*i - 48) * (*j - 48) + carry;
+            int carry { 0 }, temp, f=0;
+            for(Iterator i=x1.number.rbegin(); i!=x1.number.rend(); ++i) {
+                for(Iterator j=x2.number.rbegin(); j!=x2.number.rend(); ++j) {
+                    temp = char_int_converter(*i) * char_int_converter(*j) + carry;
                     carry = temp/10;
-                    adder.number.push_back(temp%10 + 48);
+                    adder.number.push_back(char_int_converter(temp%10));
                 }
                 if(carry) {
-                    adder.number.push_back(carry + 48);
+                    adder.number.push_back(char_int_converter(carry));
                     carry = 0;
                 }
                 std::reverse(adder.number.begin(), adder.number.end());
-                //std::cout<<"Before Adder = "<<adder<<std::endl;
-                for(k=f; k != 1; k/=10) {
+                for(int k=1; k <= f; ++k) {
                     adder.number.push_back('0');
                 }
-                //std::cout<<"adder = "<<adder<<"Answer = "<<Answer<<"\n";
                 Answer = Answer + adder;
                 adder = largeInt();
-                f *= 10;
+                f += 1;
             }
 
             if(x1.sign != x2.sign)
@@ -87,7 +105,7 @@ namespace libbig
         largeInt x = *this;
         largeInt y = next_number;
 
-        if(x == largeInt("0") || y == largeInt("0") || x.number.length() == 0 || y.number.length() == 0) {
+        if(x.number == "0" || y.number == "0" || x.number.length() == 0 || y.number.length() == 0) {
             return largeInt("0");
         }
         else if(x.number.length() == 1 || y.number.length() == 1) {
@@ -103,7 +121,7 @@ namespace libbig
         largeInt y1 = (f == y.number.length()) ? largeInt():largeInt(y.number.substr(0, y.number.length() - f));
         largeInt x2 = (f == x.number.length()) ? x:largeInt(x.number.substr(x.number.length() - f, x.number.length()));
         largeInt y2 = (f == y.number.length()) ? y:largeInt(y.number.substr(y.number.length() - f, y.number.length()));
-
+    
         const largeInt x3 = x1 + x2;
         const largeInt y3 = y1 + y2;        
 
@@ -116,7 +134,7 @@ namespace libbig
         if(x.sign != y.sign)
             xy.sign = false;
 
-        return xy;
+        return remove_zeroes(xy);
     }
 
 

tests/operators/multiply_test.cpp

@@ -39,7 +39,37 @@ int main()
     a = libbig::largeInt("78239823648904375");
     b = libbig::largeInt("1273898653482713986555");
     c = a * b;
-    assert(c == libbig::largeInt("99669583064888522730377914524230678125"));
+    assert(c == libbig::largeInt("99669605995064285419229672514230678125"));
+
+    // Test 7
+    a = libbig::largeInt("-0");
+    b = libbig::largeInt("100");
+    c = a * b;
+    assert(c == libbig::largeInt("0"));
+
+    // Test 8
+    a = libbig::largeInt("-100");
+    b = libbig::largeInt("-100");
+    c = a * b;
+    assert(c == libbig::largeInt("10000"));
+
+    // Test 9
+    a = libbig::largeInt("0000000000000000000000000000000000000000000000000000");
+    b = libbig::largeInt("1111111111111111111111111111111111111111111111111111");
+    c = a * b;
+    assert(c == libbig::largeInt("0"));
+
+    // Test 10
+    a = libbig::largeInt("746767836578647567834567834657836587");
+    b = libbig::largeInt("89275924758922476024759846938475804579247593468034769835763597028476937");
+    c = a * b;
+    assert(c == libbig::largeInt("66668389190778655840704160824409791548824154145813767587653936294222881640592188804856387839101068044294019"));
+
+    // Test 10
+    a = libbig::largeInt("8492387957349593498354782359782345782367895623478567894235692347856789234789236789342967891235627348589234567892345234567892369287345");
+    b = libbig::largeInt("824358293475908745902350926589023459023485089347892650234650273456207349236502347524357832456789235623489759235623789456782394567892359478235239423569782356234659837562378965278956237489235");
+    c = a * b;
+    assert(c == libbig::largeInt("7000770444056069403046119404826740387252166452093943636486324185225836788920060077258109995450330997820727632474615791121779806923541276193853962113432983583426568371447855101334504301369704676060587738461922443343618487980096828486083202559107333726983966552151422667448209619250487990929538296732965889159956209059231075"));
 
     return 0;
 }