day 17

day 17/day_17_felix.cpp

+#include <bits/stdc++.h>
+using namespace std;
+const bool DEBUG = true;
+
+#define ll long long
+
+array<ll, 3> REGISTERS = {0, 0, 0};
+vector<int> OPTCODES;
+vector<int> OPERANDS;
+
+void read_input() {
+    string line;
+    int reg = 0;
+    while (getline(cin, line) && line.size() > 0) {
+        REGISTERS[reg] = stoi(line.substr(12));
+        if (DEBUG) cout << "Register " << reg << " = " << REGISTERS[reg] << endl;
+        reg++;
+    }
+    getline(cin, line);
+    if (DEBUG) cout << "Start reading optcodes from " << line << endl;
+    stringstream ss(line);
+    char comma;
+    int optcode, operand;
+    for (int i = 0; i < 8; i++) ss >> comma; //clear start
+    while (ss >> operand >> comma >> optcode) {
+        OPTCODES.push_back(optcode);
+        OPERANDS.push_back(operand);
+        if (DEBUG) cout << "  Operand " << operand << " Optcode " << optcode << endl;
+        ss >> comma;
+    }
+
+}
+
+ll part1() {
+    int i_point = 0;
+    string result = "";
+    string nocommas = "";
+    while (i_point < OPTCODES.size()) {
+        if (DEBUG) cout << "Point " << i_point << " REGISTERS: " << REGISTERS[0] << " " << REGISTERS[1] << " " << REGISTERS[2] << endl;
+        int instruction = OPERANDS[i_point];
+        int optcode = OPTCODES[i_point];
+        ll combo = optcode < 4 ? optcode : REGISTERS[optcode - 4];
+        double a;
+        if (DEBUG) cout << "  Instruction " << instruction << " Optcode " << optcode << " Combo " << combo << endl;
+        switch (instruction) {
+            case 0: // adv                
+                a = REGISTERS[0] / pow(2, combo);
+                REGISTERS[0] = trunc(a);
+                if (DEBUG) cout << "    ADV " << REGISTERS[0] << endl;
+                break;
+            case 1: // bxl
+                REGISTERS[1] = REGISTERS[1] ^ optcode;
+                if (DEBUG) cout << "    BXL " << REGISTERS[1] << endl;
+                break;
+            case 2: // bst
+                REGISTERS[1] = combo % 8;
+                break;
+            case 3: // jnz
+                if (DEBUG) cout << "    JNZ " << REGISTERS[0] << endl;
+                if (REGISTERS[0] != 0){
+                    i_point = optcode / 2; // divide by two as we have two things...
+                    i_point --; // to compensate the increment
+                }
+                break;
+            case 4: // bxc
+                REGISTERS[1] = REGISTERS[1] ^ REGISTERS[2];
+                if (DEBUG) cout << "    BXC " << REGISTERS[1] << endl;
+                break;
+            case 5: // out
+                result += to_string(combo % 8);
+                result += ",";
+                nocommas += to_string(combo % 8);
+                if (DEBUG) cout << "    OUT " << combo % 8 << endl;
+                break;
+            case 6: // bdv
+                a = REGISTERS[0] / pow(2, combo);
+                REGISTERS[1] = trunc(a);
+                if (DEBUG) cout << "    BDV " << REGISTERS[1] << endl;
+                break;
+            case 7: // cdv
+                a = REGISTERS[0] / pow(2, combo);
+                REGISTERS[2] = trunc(a);
+                if (DEBUG) cout << "    CDV " << REGISTERS[2] << endl;
+                break;
+        }
+        i_point ++;
+    }
+    cout << result << endl;
+    cout << nocommas << endl;
+    
+    return stoll(nocommas);
+}
+
+int main () {
+    read_input();
+    part1();
+    return 0;
+}
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day 17/day_17_felix_part2.cpp

+#include <bits/stdc++.h>
+using namespace std;
+const bool DEBUG = true;
+#define ll long long
+
+vector<int> PROGRAM = {2,4,1,1,7,5,4,7,1,4,0,3,5,5,3,0};
+
+ll find_previous_A(int point, ll A) {
+    ll Aprev;
+    ll B, C;
+    if (point < 0) return A;
+    string debugspacs(16-point, ' ');
+    for (int a = 0; a < pow(2,3); a++) {
+        Aprev = pow(2,3)*A + a;
+        //cout << "  Testing Aprev " << Aprev << endl;
+        B = Aprev % 8;
+        B = B ^ 1;
+        C = trunc(Aprev / pow(2, B));
+        B = B ^ C;
+        B = B ^ 4;
+        B = B % 8; // mod 8 before printing in the out-command
+        //cout << "  Resulted in B " << B << endl;
+        if (B == PROGRAM[point]) {
+            cout << debugspacs << "Point " << point << " Aprev " << Aprev << " B " << B << " C " << C << endl;
+            ll result = find_previous_A(point - 1, Aprev);
+            if (result != -1) return result;
+        }   
+    }
+    return -1;
+}
+
+int main () {
+    
+    cout << find_previous_A(PROGRAM.size() - 1, 0) << endl;
+
+    return 0;
+}
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