# Project Euler 068
# Magic 5-gon ring: maximum 16-digit magic string.
extern {
function calloc(n: i64, size: i64) -> ptr<void>
function free(p: ptr<void>) -> void
}
function swap(a: ptr<i32>, i: i32, j: i32) -> void {
let t: i32 = a[i]
a[i] = a[j]
a[j] = t
}
function next_perm(a: ptr<i32>, n: i32) -> bool {
let mut i: i32 = n - 2
while i >= 0 && a[i] >= a[i + 1] { i = i - 1 }
if i < 0 { return false }
let mut j: i32 = n - 1
while a[j] <= a[i] { j = j - 1 }
swap(a, i, j)
let mut l: i32 = i + 1
let mut r: i32 = n - 1
while l < r {
swap(a, l, r)
l = l + 1
r = r - 1
}
return true
}
function append_num(v: i64, x: i32) -> i64 {
if x >= 10 {
return v * 100 + (x as i64)
}
return v * 10 + (x as i64)
}
function main() -> i32 {
let nums: ptr<i32> = calloc(10, 4)
let outer: ptr<i32> = calloc(5, 4)
let inner: ptr<i32> = calloc(5, 4)
if nums == null || outer == null || inner == null { return 1 }
let mut i: i32 = 0
for i in 0..10 {
nums[i] = i + 1
}
let mut best: i64 = 0
while true {
for i in 0..5 {
outer[i] = nums[i]
inner[i] = nums[i + 5]
}
let mut has10: bool = false
for i in 0..5 {
if outer[i] == 10 { has10 = true }
}
if has10 {
let s0: i32 = outer[0] + inner[0] + inner[1]
let mut magic: bool = true
i = 1
while i < 5 {
let nidx: i32 = i + 1
if nidx == 5 { nidx = 0 }
if outer[i] + inner[i] + inner[nidx] != s0 {
magic = false
break
}
i = i + 1
}
if magic {
let mut start: i32 = 0
for i in 1..5 {
if outer[i] < outer[start] { start = i }
}
let mut v: i64 = 0
let mut digs: i32 = 0
for i in 0..5 {
let mut idx: i32 = start + i
if idx >= 5 { idx = idx - 5 }
let a: i32 = outer[idx]
let b: i32 = inner[idx]
let mut cidx: i32 = idx + 1
if cidx >= 5 { cidx = 0 }
let c: i32 = inner[cidx]
if a >= 10 { digs = digs + 2 } else { digs = digs + 1 }
digs = digs + 2
v = append_num(v, a)
v = append_num(v, b)
v = append_num(v, c)
}
if digs == 16 && v > best {
best = v
}
}
}
if !next_perm(nums, 10) { break }
}
printf("%lld\n", best)
free(inner)
free(outer)
free(nums)
return 0
}
Generated C
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* Flow runtime helpers */
typedef struct flow_temp_node { struct flow_temp_node* next; } flow_temp_node;
static flow_temp_node* flow_temp_head = NULL;
static int flow_temp_atexit_set = 0;
__attribute__((unused)) static void flow_temp_free_all(void) {
while (flow_temp_head) {
flow_temp_node* n = flow_temp_head;
flow_temp_head = n->next;
free(n);
}
}
__attribute__((unused)) static void* flow_temp_alloc(size_t nbytes) {
flow_temp_node* node = (flow_temp_node*)malloc(sizeof(flow_temp_node) + nbytes);
if (!node) return NULL;
node->next = flow_temp_head;
flow_temp_head = node;
if (!flow_temp_atexit_set) {
flow_temp_atexit_set = 1;
atexit(flow_temp_free_all);
}
return (void*)(node + 1);
}
#ifndef FLOW_DIAG
#define FLOW_DIAG(msg) fprintf(stderr, "%s", (msg))
#endif
#ifndef FLOW_LOG
#define FLOW_LOG(fmt, ...) printf(fmt, __VA_ARGS__)
#endif
#ifndef FLOW_LOG_EMPTY
#define FLOW_LOG_EMPTY(fmt) printf(fmt)
#endif
static char* flow_strcat(const char* a, const char* b) {
size_t la = strlen(a ? a : ""), lb = strlen(b ? b : "");
char* r = (char*)flow_temp_alloc(la + lb + 1);
if (!r) return NULL;
if (la) memcpy(r, a, la);
if (lb) memcpy(r + la, b, lb);
r[la + lb] = '\0';
return r;
}
#define __flow_in_arr(arr, val) __extension__ ({ \
int _found = 0; \
size_t _n = sizeof(arr)/sizeof((arr)[0]); \
for (size_t _i = 0; _i < _n; _i++) { \
if ((arr)[_i] == (val)) { _found = 1; break; } \
} _found; })
/* Unified fault handler (MISRA #279) — override with -DFLOW_FAULT_HANDLER=fn */
#ifndef FLOW_FAULT_HANDLER
__attribute__((unused)) static inline void flow_fault_handler(const char* msg) {
fprintf(stderr, "flow: %s\n", msg ? msg : "fault");
abort();
#if defined(__GNUC__) || defined(__clang__)
__builtin_unreachable();
#endif
}
#else
#define flow_fault_handler FLOW_FAULT_HANDLER
#endif
#define flow_div_by_zero_handler() flow_fault_handler("division by zero")
#define flow_shift_ub_handler() flow_fault_handler("invalid shift (amount out of range or left-shift of negative)")
#ifndef FLOW_CHECKED_DIV
#define FLOW_CHECKED_DIV(L, R) (((R) != 0) ? ((L) / (R)) : (flow_div_by_zero_handler(), (L) * 0))
#endif
#ifndef FLOW_CHECKED_MOD
#define FLOW_CHECKED_MOD(L, R) (((R) != 0) ? ((L) % (R)) : (flow_div_by_zero_handler(), (L) * 0))
#endif
#ifndef FLOW_CHECKED_SHL
#define FLOW_CHECKED_SHL(L, R) ((((R) >= 0) && ((unsigned long long)(R) < (sizeof(L) * 8ull)) && ((L) >= 0)) ? ((L) << (R)) : (flow_shift_ub_handler(), (L) * 0))
#endif
#ifndef FLOW_CHECKED_SHR
#define FLOW_CHECKED_SHR(L, R) ((((R) >= 0) && ((unsigned long long)(R) < (sizeof(L) * 8ull))) ? ((L) >> (R)) : (flow_shift_ub_handler(), (L) * 0))
#endif
#include <math.h>
void* _ui_state = NULL;
static inline float i32_to_f32(int32_t v) { return (float)v; }
/* Host stub for @gpu kernels (device codegen replaces this). */
static inline int32_t gpu_thread_id(void) { return 0; }
void swap_ptr_i32_i32_i32(int32_t* a, int32_t i, int32_t j);
bool next_perm_ptr_i32_i32(int32_t* a, int32_t n);
int64_t append_num_i64_i32(int64_t v, int32_t x);
int32_t main(void);
void swap_ptr_i32_i32_i32(int32_t* a, int32_t i, int32_t j) {
int32_t t = a[i];
a[i] = a[j];
a[j] = t;
}
bool next_perm_ptr_i32_i32(int32_t* a, int32_t n) {
int32_t i = (n - 2);
while ((i >= 0 && a[i] >= a[(i + 1)])) {
i = (i - 1);
}
if (i < 0) {
return 0;
}
int32_t j = (n - 1);
while (a[j] <= a[i]) {
j = (j - 1);
}
swap_ptr_i32_i32_i32(a, i, j);
int32_t l = (i + 1);
int32_t r = (n - 1);
while (l < r) {
swap_ptr_i32_i32_i32(a, l, r);
l = (l + 1);
r = (r - 1);
}
return 1;
}
int64_t append_num_i64_i32(int64_t v, int32_t x) {
if (x >= 10) {
return ((v * 100) + ((int64_t)(x)));
}
return ((v * 10) + ((int64_t)(x)));
}
int32_t main(void) {
int32_t* nums = (int32_t*)(calloc(10, 4));
int32_t* outer = (int32_t*)(calloc(5, 4));
int32_t* inner = (int32_t*)(calloc(5, 4));
if (((nums == NULL || outer == NULL) || inner == NULL)) {
return 1;
}
int32_t i = 0;
int32_t __flow_step_1 = 1;
for (int32_t i = 0; (0 <= 10) ? i < 10 : i > 10; i += (0 <= 10) ? 1 : -1) {
nums[i] = (i + 1);
}
int64_t best = 0;
while (1) {
int32_t __flow_step_2 = 1;
for (int32_t i = 0; (0 <= 5) ? i < 5 : i > 5; i += (0 <= 5) ? 1 : -1) {
outer[i] = nums[i];
inner[i] = nums[(i + 5)];
}
bool has10 = 0;
int32_t __flow_step_3 = 1;
for (int32_t i = 0; (0 <= 5) ? i < 5 : i > 5; i += (0 <= 5) ? 1 : -1) {
if (outer[i] == 10) {
has10 = 1;
}
}
if (has10) {
int32_t s0 = ((outer[0] + inner[0]) + inner[1]);
bool magic = 1;
i = 1;
while (i < 5) {
int32_t nidx = (i + 1);
if (nidx == 5) {
nidx = 0;
}
if (((outer[i] + inner[i]) + inner[nidx]) != s0) {
magic = 0;
break;
}
i = (i + 1);
}
if (magic) {
int32_t start = 0;
int32_t __flow_step_4 = 1;
for (int32_t i = 1; (1 <= 5) ? i < 5 : i > 5; i += (1 <= 5) ? 1 : -1) {
if (outer[i] < outer[start]) {
start = i;
}
}
int64_t v = 0;
int32_t digs = 0;
int32_t __flow_step_5 = 1;
for (int32_t i = 0; (0 <= 5) ? i < 5 : i > 5; i += (0 <= 5) ? 1 : -1) {
int32_t idx = (start + i);
if (idx >= 5) {
idx = (idx - 5);
}
int32_t a = outer[idx];
int32_t b = inner[idx];
int32_t cidx = (idx + 1);
if (cidx >= 5) {
cidx = 0;
}
int32_t c = inner[cidx];
if (a >= 10) {
digs = (digs + 2);
} else {
digs = (digs + 1);
}
digs = (digs + 2);
v = append_num_i64_i32(v, a);
v = append_num_i64_i32(v, b);
v = append_num_i64_i32(v, c);
}
if ((digs == 16 && v > best)) {
best = v;
}
}
}
if ((!(next_perm_ptr_i32_i32(nums, 10)))) {
break;
}
}
printf("%lld\n", best);
free(inner);
free(outer);
free(nums);
return 0;
}