# Project Euler 653
# Frictionless tube: d(10^9, 10^6+1, 500001).
extern {
function calloc(n: i64, size: i64) -> ptr<void>
function free(p: ptr<void>) -> void
}
function heapify(a: ptr<i64>, n: i64, i0: i64) -> void {
let mut i: i64 = i0
while true {
let mut largest: i64 = i
let l: i64 = 2 * i + 1
let r: i64 = 2 * i + 2
if l < n && a[l] > a[largest] { largest = l }
if r < n && a[r] > a[largest] { largest = r }
if largest == i { break }
let t: i64 = a[i]
a[i] = a[largest]
a[largest] = t
i = largest
}
}
function heapsort(a: ptr<i64>, n: i64) -> void {
let mut i: i64 = n / 2 - 1
while i >= 0 {
heapify(a, n, i)
i = i - 1
}
i = n - 1
while i > 0 {
let t: i64 = a[0]
a[0] = a[i]
a[i] = t
heapify(a, i, 0)
i = i - 1
}
}
function d(L: i64, N: i64, j: i64) -> i64 {
let MOD: i64 = 32745673
let mut r: i64 = 6563116
let a: ptr<i64> = calloc(N, 8)
if a == null { return -1 }
let mut y: i64 = 0
let mut i: i64 = 0
while i < N {
let g: i64 = (r % 1000) + 1
y = y + g
if r <= 10000000 {
a[i] = 0 - y
} else {
a[i] = y
}
r = (r * r) % MOD
i = i + 1
}
heapsort(a, N)
let m: i64 = N - j + 1
let am: i64 = a[m - 1]
free(a)
return (L - 20 * j + 10) + am
}
function main() -> i32 {
printf("%lld\n", d(1000000000, 1000001, 500001))
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 heapify_ptr_i64_i64_i64(int64_t* a, int64_t n, int64_t i0);
void heapsort_ptr_i64_i64(int64_t* a, int64_t n);
int64_t d_i64_i64_i64(int64_t L, int64_t N, int64_t j);
int32_t main(void);
void heapify_ptr_i64_i64_i64(int64_t* a, int64_t n, int64_t i0) {
int64_t i = i0;
while (1) {
int64_t largest = i;
int64_t l = ((2 * i) + 1);
int64_t r = ((2 * i) + 2);
if ((l < n && a[l] > a[largest])) {
largest = l;
}
if ((r < n && a[r] > a[largest])) {
largest = r;
}
if (largest == i) {
break;
}
int64_t t = a[i];
a[i] = a[largest];
a[largest] = t;
i = largest;
}
}
void heapsort_ptr_i64_i64(int64_t* a, int64_t n) {
int64_t i = (FLOW_CHECKED_DIV((n), (2)) - 1);
while (i >= 0) {
heapify_ptr_i64_i64_i64(a, n, i);
i = (i - 1);
}
i = (n - 1);
while (i > 0) {
int64_t t = a[0];
a[0] = a[i];
a[i] = t;
heapify_ptr_i64_i64_i64(a, i, 0);
i = (i - 1);
}
}
int64_t d_i64_i64_i64(int64_t L, int64_t N, int64_t j) {
int64_t MOD = 32745673;
int64_t r = 6563116;
int64_t* a = (int64_t*)(calloc(N, 8));
if (a == NULL) {
return (-1);
}
int64_t y = 0;
int64_t i = 0;
while (i < N) {
int64_t g = (FLOW_CHECKED_MOD((r), (1000)) + 1);
y = (y + g);
if (r <= 10000000) {
a[i] = (0 - y);
} else {
a[i] = y;
}
r = FLOW_CHECKED_MOD(((r * r)), (MOD));
i = (i + 1);
}
heapsort_ptr_i64_i64(a, N);
int64_t m = ((N - j) + 1);
int64_t am = a[(m - 1)];
free(a);
return (((L - (20 * j)) + 10) + am);
}
int32_t main(void) {
printf("%lld\n", d_i64_i64_i64(1000000000, 1000001, 500001));
return 0;
}