adding leetcode problems

leetcode/p263_uglynumber.cpp

@@ -0,0 +1,24 @@
+class Solution {
+public:
+    // use a non-type parameter as the template parameter list.
+    template <int F>    // F represents factor, and it has to be constant
+    // reduce factor n, has to be reference, because we want to change n.
+    void reduceFactor(int& n){
+        while(n%F==0){
+            n = n/F;
+        }
+    }
+    bool isUgly(int n) {
+        // ugly number has to be a positive integer.
+        if(n<=0){
+            return false;
+        }
+        // reduce factor 2
+        reduceFactor<2>(n);
+        // reduce factor 3
+        reduceFactor<3>(n);
+        // reduce factor 5
+        reduceFactor<5>(n);
+        return (n==1);
+    }
+};