Card shuffles: Difference between revisions
Added solution for C
(Added solution for C) |
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Allow for "human errors" of imperfect cutting and interleaving.
<br><br>
=={{header|C}}==
{{trans|Modula-2}}
<lang c>#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
void init() {
srand((unsigned int)time(NULL));
}
int random(int low, int high) {
int diff, val;
diff = high - low;
if (diff == 0) {
return low;
}
val = rand() % diff;
return val + low;
}
void initDeck(int *deck, const int size) {
int i;
for (i = 0; i < size; ++i) {
*deck++ = i + 1;
}
}
void writeDeck(const int *deck, const int size) {
int i;
printf("[");
if (size > 0) {
printf("%d", *deck++);
}
for (i = 1; i < size; ++i) {
printf(", %d", *deck++);
}
printf("]");
}
void riffleShuffle(int * const deck, const int size, int flips) {
int n, cutPoint, nlp, lp, rp, bound;
int *nl;
nl = (int *)malloc(size * sizeof(int));
for (n = 0; n < flips; ++n) {
cutPoint = size / 2;
if (random(0, 2) > 0) {
cutPoint = cutPoint + random(0, size / 10);
} else {
cutPoint = cutPoint - random(0, size / 10);
}
nlp = 0;
lp = 0;
rp = cutPoint;
while (lp < cutPoint && rp < size) {
/* Allow for an imperfect riffling so that more than one card can come from the same side in a row
biased towards the side with more cards. Remove the IF statement for perfect riffling. */
bound = (cutPoint - lp) * 50 / (size - rp);
if (random(0, 50) >= bound) {
nl[nlp++] = deck[rp++];
} else {
nl[nlp++] = deck[lp++];
}
}
while (lp < cutPoint) {
nl[nlp++] = deck[lp++];
}
while (rp < size) {
nl[nlp++] = deck[rp++];
}
memcpy(deck, nl, size * sizeof(int));
}
free(nl);
}
void overhandShuffle(int * const mainHand, const int size, int passes) {
int n, cutSize, mp, op, tp, i;
int *otherHand, *temp;
otherHand = (int *)malloc(size * sizeof(int));
temp = (int *)malloc(size * sizeof(int));
for (n = 0; n < passes; ++n) {
mp = 0;
op = 0;
tp = 0;
while (mp < size) {
cutSize = random(0, size / 5) + 1;
/* grab the next cut up to the end of the cards left in the main hand */
for (i = 0; i < cutSize && mp < size; ++i) {
temp[tp++] = mainHand[mp++];
}
/* add them to the cards in the other hand, sometimes to the fron sometimes to the back */
if (random(0, 10) >= 1) {
/* front most of the time */
/* move the elements of other hand forward to make room for temp */
for (i = op - 1; i >= 0; --i) {
otherHand[i + tp] = otherHand[i];
}
/* copy temp to the front of other hand */
memcpy(otherHand, temp, tp * sizeof(int));
op += tp;
tp = 0;
} else {
/* end sometimes */
for (i = 0; i < tp; ++i, ++op) {
otherHand[op] = temp[i];
}
tp = 0;
}
}
/* move the cards back to the main hand */
memcpy(mainHand, otherHand, size * sizeof(int));
}
free(otherHand);
free(temp);
}
#define SIZE 20
int main() {
int deck[SIZE];
init();
printf("Riffle shuffle\n");
initDeck(deck, SIZE);
writeDeck(deck, SIZE);
printf("\n");
riffleShuffle(deck, SIZE, 10);
writeDeck(deck, SIZE);
printf("\n\n");
printf("Riffle shuffle\n");
initDeck(deck, SIZE);
writeDeck(deck, SIZE);
printf("\n");
riffleShuffle(deck, SIZE, 1);
writeDeck(deck, SIZE);
printf("\n\n");
printf("Overhand shuffle\n");
initDeck(deck, SIZE);
writeDeck(deck, SIZE);
printf("\n");
overhandShuffle(deck, SIZE, 10);
writeDeck(deck, SIZE);
printf("\n\n");
printf("Overhand shuffle\n");
initDeck(deck, SIZE);
writeDeck(deck, SIZE);
printf("\n");
overhandShuffle(deck, SIZE, 1);
writeDeck(deck, SIZE);
printf("\n\n");
return 0;
}</lang>
{{out}}
<pre>Riffle shuffle
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
[1, 15, 6, 2, 11, 18, 9, 5, 3, 4, 7, 16, 13, 8, 10, 14, 19, 12, 17, 20]
Riffle shuffle
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
[1, 2, 11, 3, 4, 5, 12, 13, 6, 7, 14, 8, 15, 16, 9, 17, 10, 18, 19, 20]
Overhand shuffle
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
[2, 19, 4, 10, 11, 8, 12, 7, 6, 3, 16, 14, 18, 1, 5, 13, 9, 15, 17, 20]
Overhand shuffle
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
[20, 17, 18, 19, 14, 15, 16, 10, 11, 12, 13, 9, 8, 7, 5, 6, 1, 2, 3, 4]</pre>
=={{header|C++}}==
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