Start hw1

1 files changed, 27 insertions, 0 deletions

diff --git a/csci5271/hw1/hw1p4.c b/csci5271/hw1/hw1p4.c
new file mode 100644
index 0000000..e449de5
--- /dev/null
+++ b/csci5271/hw1/hw1p4.c
@@ -0,0 +1,27 @@
+#include <stdio.h>
+
+/* Reverse the elements from FROM to TO, inclusive */
+void reverse_range(int *a, int from, int to) {
+  unsigned int *p = &a[from];
+  unsigned int *q = &a[to];
+  /* Until the pointers move past each other: */
+  while (!(p == q + 1 || p == q + 2)) {
+    /* Swap *p with *q, without using a temporary variable */
+    *p += *q;     /* *p == P + Q */
+    *q = *p - *q; /* *q == P + Q - Q = P */
+    *p = *p - *q; /* *p == P + Q - P = Q */
+    /* Advance pointers towards each other */
+    p++;
+    q--;
+  }
+}
+int main() {
+  int a[10] = {255, 0, -65536, 2147483647, -2147483648,
+               -1,  0, 1,      2,          3};
+  reverse_range(a, 0, 9);
+  for (int i = 0; i < 10; i++) {
+    printf("%d ", a[i]);
+  }
+  printf("\n");
+  return 0;
+}
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