Data commit

Task/Random-Latin-squares/C/random-latin-squares.c

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+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+// low <= num < high
+int randInt(int low, int high) {
+    return (rand() % (high - low)) + low;
+}
+
+// shuffle an array of n elements
+void shuffle(int *const array, const int n) {
+    if (n > 1) {
+        int i;
+        for (i = 0; i < n - 1; i++) {
+            int j = randInt(i, n);
+
+            int t = array[i];
+            array[i] = array[j];
+            array[j] = t;
+        }
+    }
+}
+
+// print an n * n array
+void printSquare(const int *const latin, const int n) {
+    int i, j;
+    for (i = 0; i < n; i++) {
+        printf("[");
+        for (j = 0; j < n; j++) {
+            if (j > 0) {
+                printf(", ");
+            }
+            printf("%d", latin[i * n + j]);
+        }
+        printf("]\n");
+    }
+    printf("\n");
+}
+
+void latinSquare(const int n) {
+    int *latin, *used;
+    int i, j, k;
+
+    if (n <= 0) {
+        printf("[]\n");
+        return;
+    }
+
+    // allocate
+    latin = (int *)malloc(n * n * sizeof(int));
+    if (!latin) {
+        printf("Failed to allocate memory.");
+        return;
+    }
+
+    // initialize
+    for (i = 0; i < n; i++) {
+        for (j = 0; j < n; j++) {
+            latin[i * n + j] = j;
+        }
+    }
+
+    // first row
+    shuffle(latin, n);
+
+    // middle row(s)
+    for (i = 1; i < n - 1; i++) {
+        bool shuffled = false;
+
+        while (!shuffled) {
+            shuffle(&latin[i * n], n);
+
+            for (k = 0; k < i; k++) {
+                for (j = 0; j < n; j++) {
+                    if (latin[k * n + j] == latin[i * n + j]) {
+                        goto shuffling;
+                    }
+                }
+            }
+            shuffled = true;
+
+        shuffling: {}
+        }
+    }
+
+    //last row
+    used = (int *)malloc(n * sizeof(int));
+    for (j = 0; j < n; j++) {
+        memset(used, 0, n * sizeof(int));
+        for (i = 0; i < n - 1; i++) {
+            used[latin[i * n + j]] = 1;
+        }
+        for (k = 0; k < n; k++) {
+            if (used[k] == 0) {
+                latin[(n - 1) * n + j] = k;
+                break;
+            }
+        }
+    }
+    free(used);
+
+    // print the result
+    printSquare(latin, n);
+    free(latin);
+}
+
+int main() {
+    // initialze the random number generator
+    srand((unsigned int)time((time_t)0));
+
+    latinSquare(5);
+    latinSquare(5);
+    latinSquare(10);
+
+    return 0;
+}