diff --git a/d01.cc b/d01.cc
index 8274cd4..617a402 100644
--- a/d01.cc
+++ b/d01.cc
@@ -4,9 +4,11 @@
 
 using namespace std;
 
-vector<unsigned> parse()
+typedef vector<unsigned> Input;
+
+Input parse()
 {
-    vector<unsigned> elves;
+    Input elves;
 
     unsigned elf = 0;
     for (string line; getline(cin, line);) {
@@ -18,16 +20,16 @@ vector<unsigned> parse()
         elf += stoul(line);
     }
 
-    sort(elves.begin(), elves.end(), greater<int>());
+    sort(elves.begin(), elves.end(), greater<unsigned>());
     return elves;
 }
 
-unsigned p1(vector<unsigned> &input)
+unsigned p1(Input &input)
 {
     return input[0];
 }
 
-unsigned p2(vector<unsigned> &input)
+unsigned p2(Input &input)
 {
     return input[0] + input[1] + input[2];
 }
diff --git a/d02.cc b/d02.cc
index 9f49b94..bc6a0c3 100644
--- a/d02.cc
+++ b/d02.cc
@@ -4,9 +4,11 @@
 
 using namespace std;
 
-vector<array<unsigned, 2>> parse()
+typedef vector<array<unsigned, 2>> Input;
+
+Input parse()
 {
-    vector<array<unsigned, 2>> input;
+    Input input;
     for (string line; getline(cin, line);) {
         if (line.at(1) != ' ') throw "parse";
         unsigned oppo = line.at(0) - 'A';
@@ -17,7 +19,7 @@ vector<array<unsigned, 2>> parse()
     return input;
 }
 
-unsigned p1(vector<array<unsigned, 2>> &input)
+unsigned p1(Input &input)
 {
     unsigned score = 0;
     for (auto i : input) {
@@ -28,7 +30,7 @@ unsigned p1(vector<array<unsigned, 2>> &input)
     return score;
 }
 
-unsigned p2(vector<array<unsigned, 2>> &input)
+unsigned p2(Input &input)
 {
     unsigned score = 0;
     for (auto i : input) {
diff --git a/d03.cc b/d03.cc
index df3eaf3..48986c2 100644
--- a/d03.cc
+++ b/d03.cc
@@ -1,6 +1,7 @@
 #include <iostream>
 #include <vector>
 #include <unordered_set>
+#include <algorithm>
 
 using namespace std;
 
@@ -25,7 +26,7 @@ template<class T>
 unordered_set<T> intersect(unordered_set<T> &a, unordered_set<T> &b)
 {
     unordered_set<T> o;
-    for (auto x : a) if (b.count(x)) o.insert(x);
+    copy_if(a.begin(), a.end(), inserter(o, o.end()), [&](T i){return b.count(i);});
     return o;
 }
 
diff --git a/d04.cc b/d04.cc
index ebf80f3..d4dc58d 100644
--- a/d04.cc
+++ b/d04.cc
@@ -1,11 +1,11 @@
 #include <iostream>
 #include <vector>
 #include <array>
+#include <algorithm>
 
 using namespace std;
 
-class Range {
-public:
+struct Range {
     unsigned min;
     unsigned max;
 
@@ -35,21 +35,21 @@ Input parse()
 
 unsigned p1(const Input &input)
 {
-    unsigned count = 0;
-    for (auto i : input) if (i[0].contains(i[1]) || i[1].contains(i[0])) count++;
-    return count;
+    return count_if(input.begin(), input.end(), [](decltype(input[0]) i){
+        return i[0].contains(i[1]) || i[1].contains(i[0]);
+    });
 }
 
 unsigned p2(const Input &input)
 {
-    unsigned count = 0;
-    for (auto i : input) if (i[0].overlaps(i[1])) count++;
-    return count;
+    return count_if(input.begin(), input.end(), [](decltype(input[0]) i){
+        return i[0].overlaps(i[1]);
+    });
 }
 
 int main()
 {
-    Input input = parse();
+    auto input = parse();
     cout << p1(input) << endl;
     cout << p2(input) << endl;
 }
diff --git a/d05.cc b/d05.cc
index a0e9ece..72237d6 100644
--- a/d05.cc
+++ b/d05.cc
@@ -90,7 +90,7 @@ string p2(const Input &input)
 
 int main()
 {
-    Input input = parse();
+    auto input = parse();
     cout << p1(input) << endl;
     cout << p2(input) << endl;
 }