# Project Euler 542
# Geometric Progression with Maximum Sum — T(10^17) via piecewise S(k).
const N: i64 = 100000000000000000
function ipow128(base: i64, exp: i64) -> i128 {
let mut r: i128 = 1 as i128
let mut b: i128 = base as i128
let mut e: i64 = exp
while e > 0 {
if (e & 1) != 0 { r = r * b }
b = b * b
e = e >> 1
}
return r
}
function iroot(n: i64, k: i64) -> i64 {
if k <= 1 { return n }
if n <= 0 { return 0 }
if n == 1 { return 1 }
let mut lo: i64 = 1
let mut hi: i64 = 2
while ipow128(hi, k) <= (n as i128) {
if hi > 2000000000 { break }
hi = hi * 2
}
while lo + 1 < hi {
let mid: i64 = (lo + hi) / 2
if ipow128(mid, k) <= (n as i128) {
lo = mid
} else {
hi = mid
}
}
return lo
}
function ipow(base: i64, exp: i64) -> i64 {
let mut r: i128 = 1 as i128
let mut b: i128 = base as i128
let mut e: i64 = exp
while e > 0 {
if (e & 1) != 0 { r = r * b }
b = b * b
e = e >> 1
}
return r as i64
}
function S_val_brute(k: i64) -> i64 {
if k < 4 { return 0 }
let mut best: i64 = 0
let mut t_max: i64 = 0
let mut tmp: i64 = k
while tmp > 1 {
t_max = t_max + 1
tmp = tmp >> 1
}
let mut t: i64 = t_max
while t >= 2 {
let p_max: i64 = iroot(k, t)
if p_max < 2 {
t = t - 1
continue
}
let mut p: i64 = 2
while p <= p_max {
let d: i64 = ipow(p, t)
let b: i64 = k / d
if b == 0 { break }
let c: i64 = ipow(p, t + 1) - ipow(p - 1, t + 1)
let val: i64 = b * c
if val > best { best = val }
p = p + 1
}
t = t - 1
}
return best
}
function S_val(k: i64) -> i64 {
if k < 4 { return 0 }
if k <= 1249 { return S_val_brute(k) }
let mut best: i64 = 0
# t=3: floor-division blocking with P = k^(1/4)
let p_max3: i64 = iroot(k, 3)
if p_max3 >= 2 {
let mut P: i64 = iroot(k, 4)
if P < 2 { P = 2 }
if P > p_max3 { P = p_max3 }
let mut p: i64 = 2
while p <= P {
let d: i64 = p * p * p
let b: i64 = k / d
let c: i64 = ipow(p, 4) - ipow(p - 1, 4)
let val: i64 = b * c
if val > best { best = val }
p = p + 1
}
let Pp1: i64 = P + 1
let Pp1cubed: i64 = ipow(Pp1, 3)
let b_max: i64 = k / Pp1cubed
let mut b: i64 = 1
while b <= b_max {
let p2: i64 = iroot(k / b, 3)
if p2 >= Pp1 {
let mut pp: i64 = p2
if pp > p_max3 { pp = p_max3 }
let c: i64 = ipow(pp, 4) - ipow(pp - 1, 4)
let val: i64 = b * c
if val > best { best = val }
}
b = b + 1
}
}
# t >= 4: check all p
let mut t_max: i64 = 0
let mut tmp: i64 = k
while tmp > 1 {
t_max = t_max + 1
tmp = tmp >> 1
}
let mut t: i64 = 4
while t <= t_max {
let p_max: i64 = iroot(k, t)
if p_max >= 2 {
let mut p: i64 = 2
while p <= p_max {
let d: i64 = ipow(p, t)
let b: i64 = k / d
if b == 0 { break }
let c: i64 = ipow(p, t + 1) - ipow(p - 1, t + 1)
let val: i64 = b * c
if val > best { best = val }
p = p + 1
}
}
t = t + 1
}
return best
}
function alt_sum(a: i64, b: i64) -> i64 {
if a > b { return 0 }
let len: i64 = b - a + 1
if (len & 1) == 0 { return 0 }
if (a & 1) == 0 { return 1 }
return -1
}
function T(n: i64) -> i64 {
if n < 4 { return 0 }
let mut total: i64 = 0
let mut k: i64 = 4
while k <= n {
let v: i64 = S_val(k)
let mut step: i64 = 1
let mut hi: i64 = k + step
if hi > n { hi = n }
let mut v_hi: i64 = S_val(hi)
while v_hi == v && hi < n {
step = step * 2
hi = k + step
if hi > n { hi = n }
v_hi = S_val(hi)
}
if hi == n && v_hi == v {
total = total + v * alt_sum(k, n)
break
}
let mut lo: i64 = k + 1
let mut r: i64 = hi
while lo < r {
let mid: i64 = (lo + r) / 2
if S_val(mid) == v {
lo = mid + 1
} else {
r = mid
}
}
total = total + v * alt_sum(k, lo - 1)
k = lo
}
return total
}
function main() -> i32 {
printf("%lld\n", T(N))
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; }
__int128 ipow128_i64_i64(int64_t base, int64_t exp);
int64_t iroot_i64_i64(int64_t n, int64_t k);
int64_t ipow_i64_i64(int64_t base, int64_t exp);
int64_t S_val_brute_i64(int64_t k);
int64_t S_val_i64(int64_t k);
int64_t alt_sum_i64_i64(int64_t a, int64_t b);
int64_t T_i64(int64_t n);
int32_t main(void);
static const int64_t N = 100000000000000000;
__int128 ipow128_i64_i64(int64_t base, int64_t exp) {
__int128 r = ((__int128)(1));
__int128 b = ((__int128)(base));
int64_t e = exp;
while (e > 0) {
if ((e & 1) != 0) {
r = (r * b);
}
b = (b * b);
e = FLOW_CHECKED_SHR((e), (1));
}
return r;
}
int64_t iroot_i64_i64(int64_t n, int64_t k) {
if (k <= 1) {
return n;
}
if (n <= 0) {
return 0;
}
if (n == 1) {
return 1;
}
int64_t lo = 1;
int64_t hi = 2;
while (ipow128_i64_i64(hi, k) <= ((__int128)(n))) {
if (hi > 2000000000) {
break;
}
hi = (hi * 2);
}
while ((lo + 1) < hi) {
int64_t mid = FLOW_CHECKED_DIV(((lo + hi)), (2));
if (ipow128_i64_i64(mid, k) <= ((__int128)(n))) {
lo = mid;
} else {
hi = mid;
}
}
return lo;
}
int64_t ipow_i64_i64(int64_t base, int64_t exp) {
__int128 r = ((__int128)(1));
__int128 b = ((__int128)(base));
int64_t e = exp;
while (e > 0) {
if ((e & 1) != 0) {
r = (r * b);
}
b = (b * b);
e = FLOW_CHECKED_SHR((e), (1));
}
return ((int64_t)(r));
}
int64_t S_val_brute_i64(int64_t k) {
if (k < 4) {
return 0;
}
int64_t best = 0;
int64_t t_max = 0;
int64_t tmp = k;
while (tmp > 1) {
t_max = (t_max + 1);
tmp = FLOW_CHECKED_SHR((tmp), (1));
}
int64_t t = t_max;
while (t >= 2) {
int64_t p_max = iroot_i64_i64(k, t);
if (p_max < 2) {
t = (t - 1);
continue;
}
int64_t p = 2;
while (p <= p_max) {
int64_t d = ipow_i64_i64(p, t);
int64_t b = FLOW_CHECKED_DIV((k), (d));
if (b == 0) {
break;
}
int64_t c = (ipow_i64_i64(p, (t + 1)) - ipow_i64_i64((p - 1), (t + 1)));
int64_t val = (b * c);
if (val > best) {
best = val;
}
p = (p + 1);
}
t = (t - 1);
}
return best;
}
int64_t S_val_i64(int64_t k) {
if (k < 4) {
return 0;
}
if (k <= 1249) {
return S_val_brute_i64(k);
}
int64_t best = 0;
int64_t p_max3 = iroot_i64_i64(k, 3);
if (p_max3 >= 2) {
int64_t P = iroot_i64_i64(k, 4);
if (P < 2) {
P = 2;
}
if (P > p_max3) {
P = p_max3;
}
int64_t p = 2;
while (p <= P) {
int64_t d = ((p * p) * p);
int64_t b = FLOW_CHECKED_DIV((k), (d));
int64_t c = (ipow_i64_i64(p, 4) - ipow_i64_i64((p - 1), 4));
int64_t val = (b * c);
if (val > best) {
best = val;
}
p = (p + 1);
}
int64_t Pp1 = (P + 1);
int64_t Pp1cubed = ipow_i64_i64(Pp1, 3);
int64_t b_max = FLOW_CHECKED_DIV((k), (Pp1cubed));
int64_t b = 1;
while (b <= b_max) {
int64_t p2 = iroot_i64_i64(FLOW_CHECKED_DIV((k), (b)), 3);
if (p2 >= Pp1) {
int64_t pp = p2;
if (pp > p_max3) {
pp = p_max3;
}
int64_t c = (ipow_i64_i64(pp, 4) - ipow_i64_i64((pp - 1), 4));
int64_t val = (b * c);
if (val > best) {
best = val;
}
}
b = (b + 1);
}
}
int64_t t_max = 0;
int64_t tmp = k;
while (tmp > 1) {
t_max = (t_max + 1);
tmp = FLOW_CHECKED_SHR((tmp), (1));
}
int64_t t = 4;
while (t <= t_max) {
int64_t p_max = iroot_i64_i64(k, t);
if (p_max >= 2) {
int64_t p = 2;
while (p <= p_max) {
int64_t d = ipow_i64_i64(p, t);
int64_t b = FLOW_CHECKED_DIV((k), (d));
if (b == 0) {
break;
}
int64_t c = (ipow_i64_i64(p, (t + 1)) - ipow_i64_i64((p - 1), (t + 1)));
int64_t val = (b * c);
if (val > best) {
best = val;
}
p = (p + 1);
}
}
t = (t + 1);
}
return best;
}
int64_t alt_sum_i64_i64(int64_t a, int64_t b) {
if (a > b) {
return 0;
}
int64_t len = ((b - a) + 1);
if ((len & 1) == 0) {
return 0;
}
if ((a & 1) == 0) {
return 1;
}
return (-1);
}
int64_t T_i64(int64_t n) {
if (n < 4) {
return 0;
}
int64_t total = 0;
int64_t k = 4;
while (k <= n) {
int64_t v = S_val_i64(k);
int64_t step = 1;
int64_t hi = (k + step);
if (hi > n) {
hi = n;
}
int64_t v_hi = S_val_i64(hi);
while ((v_hi == v && hi < n)) {
step = (step * 2);
hi = (k + step);
if (hi > n) {
hi = n;
}
v_hi = S_val_i64(hi);
}
if ((hi == n && v_hi == v)) {
total = (total + (v * alt_sum_i64_i64(k, n)));
break;
}
int64_t lo = (k + 1);
int64_t r = hi;
while (lo < r) {
int64_t mid = FLOW_CHECKED_DIV(((lo + r)), (2));
if (S_val_i64(mid) == v) {
lo = (mid + 1);
} else {
r = mid;
}
}
total = (total + (v * alt_sum_i64_i64(k, (lo - 1))));
k = lo;
}
return total;
}
int32_t main(void) {
printf("%lld\n", T_i64(N));
return 0;
}