1 files changed, 51 insertions, 0 deletions

diff --git a/2024/07/day07b.cpp b/2024/07/day07b.cpp
new file mode 100644
index 0000000..1c2d900
--- /dev/null
+++ b/2024/07/day07b.cpp
@@ -0,0 +1,51 @@
+#include <algorithm>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <vector>
+using namespace std;
+
+long long uncat(long long x, long long y) {
+        if (y == 0)
+                return x % 10 == 0 ? x / 10 : -1;
+        while (y > 0) {
+                if (x % 10 != y % 10)
+                        return -1;
+                x /= 10;
+                y /= 10;
+        }
+        return x;
+}
+
+bool possible(long long x, vector<long long>& a, int i) {
+        if (i == 0)
+                return a[0] == x;
+
+        bool p = possible(x-a[i], a, i-1);
+        if (a[i] != 0 && x % a[i] == 0)
+                p = p || possible(x/a[i], a, i-1);
+        auto u = uncat(x, a[i]);
+        if (u != -1)
+                p = p || possible(u, a, i-1);
+        return p;
+}
+
+int main() {
+        string line;
+        long long tot = 0;
+        while (getline(cin, line)) {
+                long long x, i;
+                vector<long long> a;
+                stringstream s(line);
+                s >> x;
+                char colon;
+                s >> colon;
+                while (s >> i)
+                        a.push_back(i);
+                if (possible(x, a, a.size()-1))
+                        tot += x;
+        }
+        cout << tot << endl;
+        return 0;
+}