add math divide

xiaoningning · xiaoningning · commit 58579b64792e · 2012-07-15T11:25:07.000-07:00
diff --git a/MathOps/src/MathOps.java b/MathOps/src/MathOps.java
@@ -1,79 +1,90 @@
+/*
+After test, there is bug for value -2147483648 (the minimus integer);
+as for integer -(-2147483648) is still -2147483648, not 2147483648.
+So we need a larger type which could contains value 2147483648
+typedef long long_int;
 
+if the sizeof(long) is equal to sizeof(int) in some system,
+you may need to use long long instead
+
+typedef long long long_int;
+
+ */
 
 public class MathOps {
 
-    public static int add(int x, int y){
+    public static int add(int x, int y) {
 
-        if(y==0) return x;
-        int a = x^y;        // add
-        int b = (x&y)<<1;   // carry
+        if (y == 0) return x;
+        int a = x ^ y;        // add
+        int b = (x & y) << 1;   // carry
         return add(a, b);
     }
 
-    public static double sqrt(double x){
+    public static double sqrt(double x) {
 
         double y = x;
         double e = 1e-15;
 
-        while(Math.abs(x/y - y) > e*y){
-            y = (x/y+y)/2.0;
+        while (Math.abs(x / y - y) > e * y) {
+            y = (x / y + y) / 2.0;
         }
         return y;
     }
 
-    public static double pow(double x, int y){
-        if (y==0) return 1;
-        if (y==1) return x;
+    public static double pow(double x, int y) {
+        if (y == 0) return 1;
+        if (y == 1) return x;
 
         boolean negative = false;
-        if(y<0){
+        if (y < 0) {
             negative = true;
             y = -y;
         }
 
-        double r = pow(x, y/2);
-        r = r*r;
+        double r = pow(x, y / 2);
+        r = r * r;
 
-        if(y%2 != 0) r = r*x;
-        if(negative) r = 1/r;
+        if (y % 2 != 0) r = r * x;
+        if (negative) r = 1 / r;
 
         return r;
     }
 
-    public static int divide(int dividend, int divisor){
+    public static int divide(int dividend, int divisor) {
 
-        if ( divisor == 0)
+        if (divisor == 0)
             throw new ArithmeticException("divisor is 0");
 
-        boolean neg_dividend = (dividend <0);
-        boolean neg_divisor = (divisor <0);
+        boolean neg_dividend = (dividend < 0);
+        boolean neg_divisor = (divisor < 0);
 
-        if(neg_dividend)
-            dividend = (dividend^-1)+1;
-        if(neg_divisor)
-            divisor = (divisor^-1)+1;
+        if (neg_dividend)
+            dividend = (dividend ^ -1) + 1;
+        if (neg_divisor)
+            divisor = (divisor ^ -1) + 1;
 
         int result = 0;
 
-        while (dividend >= divisor){
+        while (dividend >= divisor) {
             dividend -= divisor;
             result++;
 
         }
 
-        if(neg_dividend^neg_divisor)
-            result = (result^-1)+1;
+        if (neg_dividend ^ neg_divisor)
+            result = (result ^ -1) + 1;
 
         return result;
 
     }
 
-    public static void main(String[] args){
+    public static void main(String[] args) {
 
         System.out.println("add: " + add(6, -2));
         System.out.println("sqrt: " + sqrt(120.0));
-        System.out.println("pow: " + pow(2.0,-3));
-        System.out.println("divide: " + divide(-21474,3));
+        System.out.println("pow: " + pow(2.0, -3));
+        System.out.println("divide: " + divide(-21474, 3));
 
     }
 }
