feat(calc_lib): 大数减法, 只实现了整数

calc_lib/include/khl_calc/khl_calc_decimal.h

@@ -9,7 +9,9 @@ KHL_CALC_NAMESPACE_BEGIN
 class DllExport Decimal
 {
 public:
-    std::string add(std::string num1, std::string num2);
+    std::string add(std::string x, std::string y);
+
+    std::string substract(std::string x, std::string y);
 };
 KHL_CALC_NAMESPACE_END
 #endif // _KHL_CALC_DECIMAL_H_
\ No newline at end of file

calc_lib/src/khl_calc/khl_calc_decimal.cpp

@@ -5,29 +5,29 @@
 
 KHL_CALC_NAMESPACE_BEGIN
 
-std::string Decimal::add(std::string num1, std::string num2)
+std::string Decimal::add(std::string x, std::string y)
 {
     /**
      * 对齐数字
      * x = 123 , y = 4567
      * x = 0123 , y = 4567
      */
-    if (num1.size() != num2.size())
+    if (x.size() != y.size())
     {
-        if (num1.size() > num2.size())
+        if (x.size() > y.size())
         {
-            auto len = num1.size() - num2.size();
+            auto len = x.size() - y.size();
             for (int i = 0; i < len; i++)
             {
-                num2.insert(0, "0");
+                y.insert(0, "0");
             }
         }
         else
         {
-            auto len = num2.size() - num1.size();
+            auto len = y.size() - x.size();
             for (int i = 0; i < len; i++)
             {
-                num1.insert(0, "0");
+                x.insert(0, "0");
             }
         }
     }
@@ -37,9 +37,9 @@ std::string Decimal::add(std::string num1, std::string num2)
      * x = 0123 , y = 4567
      * x = 3210 , y = 7654
      */
-    char *sx = const_cast<char *>(num1.c_str());
-    char *sy = const_cast<char *>(num2.c_str());
-    const size_t len = num1.size();
+    char *sx = const_cast<char *>(x.c_str());
+    char *sy = const_cast<char *>(y.c_str());
+    const size_t len = x.size();
     auto a = std::make_unique<int[]>(len);
     auto b = std::make_unique<int[]>(len);
 
@@ -71,11 +71,109 @@ std::string Decimal::add(std::string num1, std::string num2)
     /** 翻转计算结果 */
     std::string str;
     int i = size - 1;
-    if(0 == c[i])
+    if (0 == c[i])
     {
         i--;
     }
-    while( i >= 0 )    
+    while (i >= 0)
+    {
+        str.push_back(c[i] + '0');
+        i--;
+    }
+
+    return str;
+}
+
+std::string Decimal::substract(std::string x, std::string y)
+{
+    // 结果是否为负数
+    bool isNegativeNumber = false;
+
+    /**
+     * 对齐数字
+     * x = 123 , y = 4567
+     * x = 0123 , y = 4567
+     */
+    if (x.size() != y.size())
+    {
+        if (x.size() > y.size())
+        {
+            auto len = x.size() - y.size();
+            for (int i = 0; i < len; i++)
+            {
+                y.insert(0, "0");
+            }
+        }
+        else
+        {
+            auto len = y.size() - x.size();
+            for (int i = 0; i < len; i++)
+            {
+                x.insert(0, "0");
+            }
+        }
+    }
+
+    /**
+     * 数字排序
+     * s1 为较大数字
+     * s2 为较小数字
+     */
+    std::string s1 = x;
+    std::string s2 = y;
+    if (s1.compare(s2) < 0)
+    {
+        s1 = y;
+        s2 = x;
+        isNegativeNumber = true;
+    }
+
+    /**
+     * 对齐后的字符串转换为倒置的 int 数组
+     * x = 0123 , y = 4567
+     * x = 3210 , y = 7654
+     */
+    char *sx = const_cast<char *>(s1.c_str());
+    char *sy = const_cast<char *>(s2.c_str());
+    const size_t len = s1.size();
+    auto a = std::make_unique<int[]>(len);
+    auto b = std::make_unique<int[]>(len);
+
+    for (int i = 0; i < len; i++)
+    {
+        a[len - 1 - i] = sx[i] - '0';
+    }
+
+    for (int i = 0; i < len; i++)
+    {
+        b[len - 1 - i] = sy[i] - '0';
+    }
+
+    /** 计算 */
+    const size_t size = len;
+    auto c = std::make_unique<int[]>(size);
+    for (int i = 0; i < len; i++)
+    {
+        // 借位处理
+        if (a[i] < b[i])
+        {
+            a[i + 1]--;
+            a[i] += 10;
+        }
+        c[i] = a[i] - b[i];
+    }
+
+    /** 翻转计算结果 */
+    std::string str;
+    int i = len - 1;
+    while(0 == c[i] && i > 1)
+    {
+        i--;
+    }
+    if( isNegativeNumber){
+        str.push_back('-');
+    }
+    while(i >= 0 )
     {
         str.push_back(c[i] + '0');
         i--;

calc_lib/test/testmain.cpp

@@ -19,10 +19,18 @@ TEST_CASE("test_add")
         std::cout << decimal->add("465465465464", "1321654876135138468135135") << std::endl;
         std::cout << "===================" << std::endl;
     }
-    
-    
-    // std::cout << decimal->add("1", "12") << std::endl;
-    // std::cout << decimal->add("1", "10") << std::endl;
-    // std::cout << decimal->add("12", "1") << std::endl;
-    // std::cout << decimal->add("10", "1") << std::endl;
+}
+
+TEST_CASE("test_substract")
+{
+    spdlog::info("test substract");
+    auto decimal = std::make_unique<khl::calc::Decimal>();
+
+    std::cout << decimal->substract("0", "0") << std::endl;
+    std::cout << decimal->substract("0", "1") << std::endl;
+    std::cout << decimal->substract("1", "0") << std::endl;
+    std::cout << decimal->substract("123", "123") << std::endl;
+    std::cout << decimal->substract("123", "4567") << std::endl;
+    std::cout << decimal->substract("4567", "123") << std::endl;
+    std::cout << decimal->substract("684651316546", "46513516846165") << std::endl;
 }