Add Day 1 solution and input for AoC 2025

Added AoC_d01.c implementing the Day 1 puzzle solution for Advent of Code 2025, including logic for parsing instructions, dial manipulation, and password calculation. Also added input.txt containing the puzzle input data.

Author: Celeste-VANDAMME

programs/2025/d01/AoC_d01.c

@@ -0,0 +1,166 @@
+// DESIGNED FOR C23.
+// @celeste_vandamme (github)
+
+/// --- LIBRARIES
+#include <stdio.h>
+#include <stdlib.h>
+
+
+/// --- STRUCTURES
+typedef struct Instruction {
+    char direction;      // L or R
+    unsigned short int degree;    // Amount of rotation/click in said direction
+} Instruction;
+
+
+/// --- FUNCTIONS PROTOTYPES
+int int_wrapper(const int value, const int min, const int max) ;
+void password_0x434C49434B(int *password, const int dial_pos, const Instruction line_instruction) ;
+
+/// --- MAIN
+int main(void)
+{
+    // --- 1. Major variables
+    const bool debug_mode = false ;
+    constexpr int initial_dial_pos = 50 ;
+    const char file_directory[100] = "input.txt" ;
+    const int line_max_size = 100 ;
+
+    // --- 2. Variables
+    int final_password = 0 ;
+    int final_password_0x434C49434B = 0 ;
+    int dial_pos = initial_dial_pos ;
+
+    int i = 0;
+    Instruction line_instruction ;
+
+    FILE *input_file = NULL ;
+    char line_input[line_max_size] ;
+
+
+    // --- 2. Process
+    input_file = fopen(file_directory, "r" );
+
+    if (input_file == NULL)
+    {
+        printf(">> File not found/an error happened.\n"
+               "Please make sure the file_directory variable is set correctly.\n\n"
+               "Directory: '%s'\n", file_directory ) ;
+
+        return EXIT_FAILURE ;
+    }
+
+    else
+    {
+        /// --- 2.a. Reading the input.txt data
+        while ( fgets(line_input, line_max_size, input_file) != NULL )
+        {
+
+            if (debug_mode) {
+                printf("\n>>> %s", line_input ) ;
+            }
+
+            // Direction: 'L' or 'R'
+            line_instruction.direction = line_input[0] ;
+
+            // Degree of rotation?
+            line_instruction.degree = 0 ;
+
+            for (i=1; line_input[i] != '\n'; i++)
+            {
+                // Make space for the new value -&- Convert '4' to 4 (char > int)
+                line_instruction.degree = (line_instruction.degree * 10) + (line_input[i] - '0') ;
+            }
+
+            if (debug_mode)
+            {
+                printf("direction = '%c' / value = '%i'\n", line_instruction.direction, line_instruction.degree) ;
+            }
+
+            /// 2. d. "Real" password with the method: "0x434C49434B"
+            password_0x434C49434B(
+                    &final_password_0x434C49434B,
+                    dial_pos,
+                    line_instruction
+                    ) ;
+
+            if (debug_mode)
+            {
+                printf("Password v2 end: %i\n", final_password_0x434C49434B ) ;
+            }
+
+            /// --- 2.b. Applying the instruction
+            // Applying the degree to the dial...
+            dial_pos += (1 - 2 * (line_instruction.direction == 'L') ) * line_instruction.degree ;
+
+            if (debug_mode)
+            {
+                printf("Dial unwrap = %i\n", dial_pos) ;
+            }
+
+            // Then restraining the value between [0;99].
+            dial_pos = int_wrapper(dial_pos, 0, 99) ;
+
+            if (debug_mode)
+            {
+                printf("dial = %i\n", dial_pos ) ;
+            }
+
+            /// 2. c. "Real" password here!
+            /// When the dial is = 0°.
+            if ( dial_pos == 0 )
+            {
+                final_password++ ;
+            }
+
+            if ( debug_mode )
+            {
+                printf("final_password = %i\n", final_password ) ;
+            }
+
+        }
+
+    }
+
+    // --- 3. Result display
+    printf("Dial position as told on the instruction:\n"
+           "DIAL = %i\n\n", dial_pos) ;
+
+    printf("Secret password:\n> '%i'\n\n", final_password);
+
+    printf("Secret password (method '0x434C49434B'):\n> '%i'\n\n", final_password_0x434C49434B);
+
+    // --- 4. End of program
+    return 0;
+}
+
+/// --- FUNCTIONS
+
+int int_wrapper(const int value, const int min, const int max)
+{
+    const int range = max - min + 1;
+    return ((((value - min) % range) + range) % range) + min ;
+}
+
+void password_0x434C49434B(int *password, int dial_pos, const Instruction line_instruction)
+{
+    //
+    const bool wasAtZero = (dial_pos == 0) ;
+
+    // Applying the instruction but not wrapping it directly.
+    dial_pos += (1 - 2 * (line_instruction.direction == 'L') ) * line_instruction.degree ;
+
+
+    // We add ONE CLICK, then we check whether we still go above 100? (+1 click each time)
+    if (dial_pos <= 0 )
+    {
+        if ( !wasAtZero )
+        {
+            *password += 1 ;
+        }
+
+        dial_pos = abs(dial_pos) ;
+    }
+
+    *password += dial_pos / 100 ;
+}