all tasks

Task/Sorting-algorithms-Merge-sort/Pascal/sorting-algorithms-merge-sort.pascal

@@ -0,0 +1,84 @@
+program MergeSortDemo;
+
+type
+  TIntArray = array of integer;
+
+function merge(left, right: TIntArray): TIntArray;
+  var
+    i, j: integer;
+  begin
+    j := 0;
+    setlength(merge, length(left) + length(right));
+    while (length(left) > 0) and (length(right) > 0) do
+    begin
+      if left[0] <= right[0] then
+      begin
+	merge[j] := left[0];
+	inc(j);
+	for i := low(left) to high(left) - 1 do
+	  left[i] := left[i+1];
+	setlength(left, length(left) - 1);
+      end
+      else
+      begin
+	merge[j] := right[0];
+	inc(j);
+	for i := low(right) to high(right) - 1 do
+	  right[i] := right[i+1];
+	setlength(right, length(right) - 1);
+      end;
+    end;
+    if length(left) > 0 then
+      for i := low(left) to high(left) do
+	  merge[j + i] := left[i];
+    j := j + length(left);
+    if length(right) > 0 then
+      for i := low(right) to high(right) do
+	  merge[j + i] := right[i];
+  end;
+
+function mergeSort(m: TIntArray): TIntArray;
+  var
+    left, right: TIntArray;
+    i, middle: integer;
+  begin
+    setlength(mergeSort, length(m));
+    if length(m) = 1 then
+      mergeSort[0] := m[0]
+    else if length(m) > 1 then
+    begin
+      middle := length(m) div 2;
+      setlength(left, middle);
+      setlength(right, length(m)-middle);
+      for i := low(left) to high(left) do
+        left[i] := m[i];
+      for i := low(right) to high(right) do
+        right[i] := m[middle+i];
+      left  := mergeSort(left);
+      right := mergeSort(right);
+      mergeSort := merge(left, right);
+    end;
+  end;
+
+var
+  data: TIntArray;
+  i: integer;
+
+begin
+  setlength(data, 8);
+  Randomize;
+  writeln('The data before sorting:');
+  for i := low(data) to high(data) do
+  begin
+    data[i] := Random(high(data));
+    write(data[i]:4);
+  end;
+  writeln;
+  data := mergeSort(data);
+  writeln('The data after sorting:');
+  for i := low(data) to high(data) do
+  begin
+    write(data[i]:4);
+  end;
+  writeln;
+end.