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Ackermann function in recursive and non-recursive form
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#include <assert.h> | |
#include <stdio.h> | |
#include <stdint.h> | |
#include <stdlib.h> | |
int ack_recursive(int m, int n) { | |
if (m == 0) { | |
return n + 1; | |
} | |
if (n == 0) { | |
return ack_recursive(m - 1, 1); | |
} | |
return ack_recursive(m - 1, ack_recursive(m, n - 1)); | |
} | |
int ack_nonrecursive(int m, int n, int *status) { | |
int value[n]; | |
size_t size = 0; | |
for (;;) { | |
if (m == 0) { | |
n++; | |
if (size-- == 0) { | |
*status = EXIT_SUCCESS; | |
break; | |
} | |
m = value[size]; | |
continue; | |
} | |
if (n == 0) { | |
m--; | |
n = 1; | |
continue; | |
} | |
size_t index = size++; | |
value[index] = m - 1; | |
n--; | |
} | |
return n; | |
} | |
int main(void) { | |
for (int m = 0; m < 2; m++) { | |
for (int n = 0; n < 2; n++) { | |
int status; | |
assert(ack_recursive(m, n) == ack_nonrecursive(m, n, &status) && status == EXIT_SUCCESS); | |
} | |
} | |
} |
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