Day6 & Day7

day7/c/day7.c

@@ -0,0 +1,113 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <omp.h>
+
+#define CHARS_MAX 1024
+#define MAX_EQUATIONS 32*1024
+#define MAX_EQUATION_VALUES 128
+
+typedef struct equation {
+    uint64_t result;
+    uint64_t *values;
+    int values_count;
+} equation_t;
+
+int solvable(equation_t, int);
+
+int main() {
+    char *p, *buf, c;
+
+    buf = calloc(CHARS_MAX, sizeof(char));
+    p = buf;
+
+    equation_t *equations = calloc(MAX_EQUATIONS, sizeof(equations[0]));
+    int equation_count = 0;
+
+    while ((c = getchar()) != EOF) {
+        *p++ = c;
+        if (c != '\n') {
+            continue;
+        }
+        p = buf;
+
+        sscanf(p, "%lu", &equations[equation_count].result);
+        while (*p++ != ':');
+
+        equations[equation_count].values = calloc(MAX_EQUATION_VALUES, sizeof(equations[0].values[0]));
+        do {
+            p++;
+            sscanf(p, "%lu", &equations[equation_count].values[equations[equation_count].values_count]);
+            equations[equation_count].values_count++;
+            while(*p != ' ' && *p != '\n') p++;
+        } while (*p != '\n');
+
+        memset(buf, 0, CHARS_MAX);
+        p = buf;
+        equation_count++;
+    }
+
+    free(buf);
+
+    uint64_t count = 0;
+    uint64_t count2 = 0;
+#pragma omp parallel for
+    for (int i = 0; i < equation_count; i++) {
+        if (solvable(equations[i], 0))
+#pragma omp critical
+        {
+            count += equations[i].result;
+        }
+        if (solvable(equations[i], 1))
+#pragma omp critical
+        {
+            count2 += equations[i].result;
+        }
+    }
+
+    for (int i = 0; i < equation_count; i++) {
+        free(equations[i].values);
+    }
+    free(equations);
+
+    printf("%lu\n", count);
+    printf("%lu\n", count2);
+}
+
+int solvable(equation_t equation, int concat_allowed) {
+    uint64_t sum = equation.values[0] + equation.values[1];
+    uint64_t product = equation.values[0] * equation.values[1];
+    uint64_t concat;
+    // Concat
+    char buf[128];
+    sprintf(buf, "%lu%lu", equation.values[0], equation.values[1]);
+    sscanf(buf, "%lu", &concat);
+    if (equation.values_count == 2) {
+        return (sum == equation.result) || (product == equation.result) || (concat == equation.result);
+    }
+
+    uint64_t *values_tmp = calloc(equation.values_count - 1, sizeof(values_tmp[0]));
+
+    // Add
+    values_tmp[0] = sum;
+    memcpy(values_tmp + 1, equation.values + 2, (equation.values_count - 2) * sizeof(values_tmp[0]));
+    equation_t tmp = {
+        .result = equation.result,
+        .values_count = equation.values_count - 1,
+        .values = values_tmp,
+    };
+
+    int solvable_sum = solvable(tmp, concat_allowed);
+
+    // Multiply
+    values_tmp[0] = product;
+    int solvable_product = solvable(tmp, concat_allowed);
+
+    // Concat
+    values_tmp[0] = concat;
+    int solvable_concat = concat_allowed ? solvable(tmp, 1) : 0;
+
+    free(values_tmp);
+    return solvable_sum || solvable_product || solvable_concat;
+}