# Project Euler 011
# Greatest product of four adjacent numbers in the 20x20 grid.
#
# Uses Flow for-ranges throughout for clean iteration.
extern {
function fopen(path: string, mode: string) -> ptr<void>
function fgetc(f: ptr<void>) -> i32
function fclose(f: ptr<void>) -> i32
function calloc(n: i64, size: i64) -> ptr<void>
function free(p: ptr<void>) -> void
}
function read_int(f: ptr<void>) -> i32 {
let mut c: i32 = fgetc(f)
while c >= 0 && (c < 48 || c > 57) {
c = fgetc(f)
}
if c < 0 {
return -1
}
let mut v: i32 = 0
while c >= 48 && c <= 57 {
v = v * 10 + (c - 48)
c = fgetc(f)
}
return v
}
function at(grid: ptr<i32>, n: i32, r: i32, c: i32) -> i64 {
return grid[r * n + c] as i64
}
function solve(grid: ptr<i32>, n: i32, k: i32) -> i64 {
let mut best: i64 = 0
for r in 0..n {
for c in 0..n {
if c + k <= n {
let mut p: i64 = 1
for i in 0..k {
p = p * at(grid, n, r, c + i)
}
if p > best { best = p }
}
if r + k <= n {
let mut p: i64 = 1
for i in 0..k {
p = p * at(grid, n, r + i, c)
}
if p > best { best = p }
}
if r + k <= n && c + k <= n {
let mut p: i64 = 1
for i in 0..k {
p = p * at(grid, n, r + i, c + i)
}
if p > best { best = p }
}
if r + k <= n && c - k + 1 >= 0 {
let mut p: i64 = 1
for i in 0..k {
p = p * at(grid, n, r + i, c - i)
}
if p > best { best = p }
}
}
}
return best
}
function main() -> i32 {
let n: i32 = 20
let grid: ptr<i32> = calloc((n * n) as i64, 4)
if grid == null {
return 1
}
let f: ptr<void> = fopen("data/p011.txt", "r")
if f == null {
printf("failed to read data/p011.txt\n")
free(grid)
return 1
}
for i in 0..(n * n) {
let v: i32 = read_int(f)
if v < 0 {
break
}
grid[i] = v
}
fclose(f)
printf("%lld\n", solve(grid, n, 4))
free(grid)
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; }
int32_t read_int_ptr_void(void* f);
int64_t at_ptr_i32_i32_i32_i32(int32_t* grid, int32_t n, int32_t r, int32_t c);
int64_t solve_ptr_i32_i32_i32(int32_t* grid, int32_t n, int32_t k);
int32_t main(void);
int32_t read_int_ptr_void(void* f) {
int32_t c = fgetc(f);
while ((c >= 0 && (c < 48 || c > 57))) {
c = fgetc(f);
}
if (c < 0) {
return (-1);
}
int32_t v = 0;
while ((c >= 48 && c <= 57)) {
v = ((v * 10) + (c - 48));
c = fgetc(f);
}
return v;
}
int64_t at_ptr_i32_i32_i32_i32(int32_t* grid, int32_t n, int32_t r, int32_t c) {
return ((int64_t)(grid[((r * n) + c)]));
}
int64_t solve_ptr_i32_i32_i32(int32_t* grid, int32_t n, int32_t k) {
int64_t best = 0;
int32_t __flow_step_1 = 1;
for (int32_t r = 0; (0 <= n) ? r < n : r > n; r += (0 <= n) ? 1 : -1) {
int32_t __flow_step_2 = 1;
for (int32_t c = 0; (0 <= n) ? c < n : c > n; c += (0 <= n) ? 1 : -1) {
if ((c + k) <= n) {
int64_t p = 1;
int32_t __flow_step_3 = 1;
for (int32_t i = 0; (0 <= k) ? i < k : i > k; i += (0 <= k) ? 1 : -1) {
p = (p * at_ptr_i32_i32_i32_i32(grid, n, r, (c + i)));
}
if (p > best) {
best = p;
}
}
if ((r + k) <= n) {
int64_t p = 1;
int32_t __flow_step_4 = 1;
for (int32_t i = 0; (0 <= k) ? i < k : i > k; i += (0 <= k) ? 1 : -1) {
p = (p * at_ptr_i32_i32_i32_i32(grid, n, (r + i), c));
}
if (p > best) {
best = p;
}
}
if (((r + k) <= n && (c + k) <= n)) {
int64_t p = 1;
int32_t __flow_step_5 = 1;
for (int32_t i = 0; (0 <= k) ? i < k : i > k; i += (0 <= k) ? 1 : -1) {
p = (p * at_ptr_i32_i32_i32_i32(grid, n, (r + i), (c + i)));
}
if (p > best) {
best = p;
}
}
if (((r + k) <= n && ((c - k) + 1) >= 0)) {
int64_t p = 1;
int32_t __flow_step_6 = 1;
for (int32_t i = 0; (0 <= k) ? i < k : i > k; i += (0 <= k) ? 1 : -1) {
p = (p * at_ptr_i32_i32_i32_i32(grid, n, (r + i), (c - i)));
}
if (p > best) {
best = p;
}
}
}
}
return best;
}
int32_t main(void) {
int32_t n = 20;
int32_t* grid = (int32_t*)(calloc(((int64_t)((n * n))), 4));
if (grid == NULL) {
return 1;
}
void* f = (void*)(fopen("data/p011.txt", "r"));
if (f == NULL) {
printf("failed to read data/p011.txt\n");
free(grid);
return 1;
}
int32_t __flow_step_7 = 1;
for (int32_t i = 0; (0 <= (n * n)) ? i < (n * n) : i > (n * n); i += (0 <= (n * n)) ? 1 : -1) {
int32_t v = read_int_ptr_void(f);
if (v < 0) {
break;
}
grid[i] = v;
}
fclose(f);
printf("%lld\n", solve_ptr_i32_i32_i32(grid, n, 4));
free(grid);
return 0;
}