Added program to find nth Ugly Number

Dynamic Programming/Ugly number.cpp

@@ -0,0 +1,57 @@
+# include<iostream>
+using namespace std;
+
+int min(int x, int y, int z) {            //find smallest among three numbers
+   if(x < y) {
+      if(x < z)
+         return x;
+      else
+         return z;
+   }else {
+      if(y < z)
+         return y;
+      else
+         return z;
+   }
+}
+
+int getUglyNum(int n) {
+   int uglyNum[n];          // To store ugly numbers
+   int i2 = 0, i3 = 0, i5 = 0;
+
+   //find next multiple as 1*2, 1*3, 1*5
+
+   int next2mul = 2;
+   int next3mul = 3;
+   int next5mul = 5;
+   int next = 1;              //initially the ugly number is 1
+
+   uglyNum[0] = 1;
+
+   for (int i=1; i<n; i++) {
+      next = min(next2mul, next3mul, next5mul);       //find next ugly number
+      uglyNum[i] = next;
+
+      if (next == next2mul) {
+         i2++;             //increase iterator of ugly numbers whose factor is 2
+         next2mul = uglyNum[i2]*2;
+      }
+
+      if (next == next3mul) {
+         i3++;             //increase iterator of ugly numbers whose factor is 3
+         next3mul = uglyNum[i3]*3;
+      }
+
+      if (next == next5mul) {
+         i5++;              //increase iterator of ugly numbers whose factor is 5
+         next5mul = uglyNum[i5]*5;
+      }
+   }
+   return next;        //the nth ugly number
+}
+
+int main() {
+   int n;
+   cout << "Enter term: "; cin >> n;
+   cout << n << "th Ugly number is: " << getUglyNum(n) << endl;
+}