Artemis: Proposed changes for increased performance

src/algorithms/primes.cc

@@ -23,12 +23,18 @@ Primes::IsPrime(int n) {
  *  @param n Upper bound (non-inclusive) of the sum
  *  @return The sum of all prime numbers from 0 to n
  */
-int
-Primes::SumPrimes(int n) {
+int Primes::SumPrimes(int n) {
   int sum = 0;
 
-  for (int i = 0; i < n; i += 1) {
-    if (IsPrime(i)) {
+  for (int i = 2; i < n; i++) {
+    bool prime = true;
+    for (int j = 2; j * j <= i; j++) {
+      if (i % j == 0) {
+        prime = false;
+        break;
+      }
+    }
+    if (prime) {
       sum += i;
     }
   }
@@ -51,4 +57,4 @@ Primes::PrimeFactors(int n) {
     }
   }
   return factors;
-}
+}

src/algorithms/sort.cc

@@ -1,3 +1,4 @@
+#include <algorithm>
 #include "sort.h"
 
 #include <algorithm>
@@ -20,19 +21,15 @@ Sort::SortVector(std::vector<int> &v) {
  */
 void
 Sort::DutchFlagPartition(std::vector<int> &v, int pivot_value) {
-  int next_value = 0;
-
-  for (int i = 0; i < (int) v.size(); i += 1) {
-    if (v[i] < pivot_value) {
-      std::swap(v[i], v[next_value]);
-      next_value += 1;
-    }
-  }
-
-  for (int i = next_value; i < (int) v.size(); i += 1) {
-    if (v[i] == pivot_value) {
-      std::swap(v[i], v[next_value]);
-      next_value += 1;
+  int smaller = 0, equal = 0, larger = v.size();
+
+  while (equal < larger) {
+    if (v[equal] < pivot_value) {
+      std::swap(v[smaller++], v[equal++]);
+    } else if (v[equal] == pivot_value) {
+      ++equal;
+    } else {
+      std::swap(v[equal], v[--larger]);
     }
   }
 }
@@ -50,11 +47,9 @@ Sort::MaxN(std::vector<int> &v, int n) {
   // So that we don't modify the original vector
   std::vector<int> temp(v);
 
-  std::sort(temp.begin(), temp.end());
+  std::partial_sort(temp.begin(), temp.begin() + n, temp.end(), std::greater<int>());
 
-  for (int i = (int) temp.size() - 1; i >= (int) temp.size() - n; i -= 1) {
-    ret.push_back(temp[i]);
-  }
+  ret.assign(temp.begin(), temp.begin() + n);
 
   return ret;
-}
+}

src/control/double.cc

@@ -1,3 +1,4 @@
+#include <unordered_map>
 #include "double.h"
 
 /**
@@ -45,21 +46,18 @@ DoubleForLoop::SumTriangle(int n) {
  * @param v
  * @return the number of pairs in an vay
  */
-int
-DoubleForLoop::CountPairs(std::vector<int> v) {
+int DoubleForLoop::CountPairs(std::vector<int> v) {
+  std::unordered_map<int, int> numCount;
+  for (const auto& num : v) {
+    numCount[num]++;
+  }
   int count = 0;
-  for (int i = 0; i < (int) v.size(); i += 1) {
-    int nDuplicates = 0;
-    for (int j = 0; j < (int) v.size(); j += 1) {
-      if (v[i] == v[j]) {
-        nDuplicates += 1;
-      }
-    }
-    if (nDuplicates == 2) {
-      count += 1;
+  for (const auto& pair : numCount) {
+    if (pair.second == 2) {
+      count++;
     }
   }
-  return count / 2;
+  return count;
 }
 
 /**
@@ -98,4 +96,4 @@ DoubleForLoop::SumMatrix(std::vector<std::vector<int>> matrix) {
     }
   }
   return sum;
-}
+}

src/control/single.cc

@@ -6,18 +6,7 @@
  * @param n the upper bound (non-inclusive)
  * @return the sum of all integer values from 0 to n
  */
-int
-SingleForLoop::SumRange(int n) {
-  int array[n];
-  int sum = 0;
-  for (int i = 0; i < n; i += 1) {
-    array[i] = i;
-  }
-  for (int i = 0; i < n; i += 1) {
-    sum += array[i];
-  }
-  return sum;
-}
+int SingleForLoop::SumRange(int n) { int sum = 0; for (int i = 0; i < n; i += 1) { sum += i; } return sum; }
 
 /**
  * @brief Returns the maximum value in an array of size n
@@ -48,17 +37,12 @@ SingleForLoop::MaxVector(std::vector<int> &arr) {
  * @param m the modulus
  * @return the sum of all values from 0 to n that are divisible by m
  */
-int
-SingleForLoop::SumModulus(int n, int m) {
-  int array[n];
+int SingleForLoop::SumModulus(int n, int m) {
   int sum = 0;
   for (int i = 0; i < n; i += 1) {
-    array[i] = i;
-  }
-  for (int i = 0; i < n; i += 1) {
-    if (array[i] % m == 0) {
-      sum += array[i];
+    if (i % m == 0) {
+      sum += i;
     }
   }
   return sum;
-}
+}

src/datastructures/vector.cc

@@ -1,3 +1,4 @@
+#include <algorithm>
 #include "vector.h"
 
 void
@@ -24,8 +25,8 @@ OpsVector::PrintVector(std::vector<double> &v) {
  */
 std::vector<int>
 OpsVector::ModifyVector(std::vector<int> &v) {
-  for (int i = 0; i < (int) v.size(); i += 1) {
-    v.at(i) += 1;
+  for (auto &elem : v) {
+    elem += 1;
   }
   return v;
 }
@@ -59,15 +60,8 @@ std::vector<int>
 OpsVector::SortVector(std::vector<int> &v) {
   std::vector<int> ret(v);
 
-  for (int i = 0; i < (int) ret.size(); i += 1) {
-    for (int j = 0; j < (int) ret.size() - 1; j += 1) {
-      if (ret[j] > ret[j + 1]) {
-        int temp = ret[j];
-        ret[j] = ret[j + 1];
-        ret[j + 1] = temp;
-      }
-    }
-  }
+  std::sort(ret.begin(), ret.end());
+
   return ret;
 }
 
@@ -79,11 +73,7 @@ OpsVector::SortVector(std::vector<int> &v) {
  */
 std::vector<int>
 OpsVector::ReverseVector(std::vector<int> &v) {
-  std::vector<int> ret;
-
-  for (int i = (int) v.size() - 1; i >= 0; i -= 1) {
-    ret.push_back(v[i]);
-  }
+  std::vector<int> ret(v.rbegin(), v.rend());
   return ret;
 }
 
@@ -126,4 +116,4 @@ OpsVector::MergeVectors(std::vector<int> &v1, std::vector<int> &v2) {
   }
 
   return ret;
-}
+}

src/generator/genvector.cc

@@ -1,3 +1,4 @@
+#include <random>
 #include "genvector.h"
 #include <random>
 #include <vector>
@@ -10,11 +11,14 @@
  */
 std::vector<int>
 GenVector::RandomVector(int n, int m) {
-  std::vector<int> ret = std::vector<int>(n);
+  std::vector<int> ret(n);
+
+  std::random_device rd;
+  std::mt19937 gen(rd());
+  std::uniform_int_distribution<> dis(0, m-1);
 
-  srand(0);
   for (int i = 0; i < n; i += 1) {
-    ret[i] = rand() % m;
+    ret[i] = dis(gen);
   }
 
   return ret;
@@ -47,17 +51,16 @@ GenVector::RandomVectorDouble(int n, int l, int u) {
  *  @param m Upper bound (non-inclusive) of the values in the matrix
  *  @return A random square matrix of size n
  */
-std::vector<std::vector<int>>
-GenVector::RandomSquareMatrix(int n, int m) {
-  std::vector<std::vector<int>> ret = std::vector<std::vector<int>>(n);
+std::vector<std::vector<int>> GenVector::RandomSquareMatrix(int n, int m) {
+  std::vector<std::vector<int>> ret(n, std::vector<int>(n));
 
-  srand(0);
-  for (int i = 0; i < n; i += 1) {
-    ret[i] = std::vector<int>(n);
-    for (int j = 0; j < n; j += 1) {
-      ret[i][j] = rand() % m;
+  std::mt19937 gen(0);
+  std::uniform_int_distribution<> dis(0, m-1);
+  for (auto &row : ret) {
+    for (auto &elem : row) {
+      elem = dis(gen);
     }
   }
 
   return ret;
-}
+}

src/strings/strops.cc

@@ -1,14 +1,6 @@
 #include "strops.h"
 
-std::string
-StrOps::ReverseString(std::string &s) {
-  std::string ret;
-
-  for (std::string::reverse_iterator rit = s.rbegin(); rit != s.rend(); ++rit) {
-    ret.insert(ret.end(), *rit);
-  }
-  return ret;
-}
+std::string StrOps::ReverseString(std::string &s) { return std::string(s.rbegin(), s.rend()); }
 
 bool
 StrOps::IsPalindrome(const std::string &s) {
@@ -18,4 +10,4 @@ StrOps::IsPalindrome(const std::string &s) {
   }
 
   return false;
-}
+}