4 files changed, 15 insertions, 11 deletions

diff --git a/2024/09/day09a.cpp b/2024/09/day09a.cpp
index c52c8f0..80732d7 100644
--- a/2024/09/day09a.cpp
+++ b/2024/09/day09a.cpp
@@ -1,6 +1,7 @@
 #include <algorithm>
 #include <iostream>
 #include <map>
+#include <ranges>
 #include <set>
 #include <sstream>
 #include <string>
@@ -16,11 +17,11 @@ int main() {
                         a.push_back(id % 2 == 0 ? id/2 : -1); // -1 = space
 
         int j = 0;
-        for (int i = a.size()-1; i >= 0; i--) {
+        for (auto& x : a | views::reverse) {
                 while (a[j] >= 0) j++;
                 if (a[j] == -2) break;
-                a[j] = a[i];
-                a[i] = -2; // -2 = freed up
+                a[j] = x;
+                x = -2; // -2 = freed up
         }
 
         long long checksum = 0;
diff --git a/2024/09/day09b.cpp b/2024/09/day09b.cpp
index 3b1ac21..c304ed4 100644
--- a/2024/09/day09b.cpp
+++ b/2024/09/day09b.cpp
@@ -1,6 +1,7 @@
 #include <algorithm>
 #include <iostream>
 #include <map>
+#include <ranges>
 #include <set>
 #include <sstream>
 #include <string>
@@ -21,16 +22,16 @@ int main() {
                         a.push_back(id % 2 == 0 ? id/2 : -1); // -1 = space
         }
 
-        for (int i = file.size()-1; i >= 0; i--) {
+        for (auto& p : file | views::reverse) {
                 for (auto& f : freesp) {
-                        if (f.first >= file[i].first) break;
-                        if (f.second >= file[i].second) {
-                                for (int k = 0; k < file[i].second; k++) {
-                                        a[f.first+k] = a[file[i].first+k];
-                                        a[file[i].first+k] = -2;
+                        if (f.first >= p.first) break;
+                        if (f.second >= p.second) {
+                                for (int k = 0; k < p.second; k++) {
+                                        a[f.first+k] = a[p.first+k];
+                                        a[p.first+k] = -2;
                                 }
-                                f.first += file[i].second;
-                                f.second -= file[i].second;
+                                f.first += p.second;
+                                f.second -= p.second;
                                 break;
                         }
                 }
diff --git a/2024/learned.txt b/2024/learned.txt
index 86d32ff..56fa515 100644
--- a/2024/learned.txt
+++ b/2024/learned.txt
@@ -7,3 +7,4 @@ List of things I learned (or refreshed) with this year's AoC.
   to assign two variables at once with a pair of references pair<int&, int&>
 * Day 5: std::find and std::replace
 * Day 8: set::insert_range(), but it is from C++23 only
+* Day 9: std::views
diff --git a/2024/template.cpp b/2024/template.cpp
index b2fd4ec..2475ae7 100644
--- a/2024/template.cpp
+++ b/2024/template.cpp
@@ -1,6 +1,7 @@
 #include <algorithm>
 #include <iostream>
 #include <map>
+#include <ranges>
 #include <set>
 #include <sstream>
 #include <string>