Add PrintWorstCase.java

Author: nobeh

PrintWorstCase.java

@@ -0,0 +1,86 @@
+import java.util.Set;
+import java.util.HashSet;
+
+public class PrintWorstCase {
+    private static final int MIN_MERGE = 32;
+    private static final Set<Integer> WORST_CASE = new HashSet<Integer>();
+    
+    private static int minRun;
+
+    public static void main(String[] args) {
+        System.out.println(" Array size   Stack Size");
+        for(int len=MIN_MERGE; len>0; len++) {
+            int size = Math.max(JDKWorstCase(len), correctWorstCase(len));
+            if(!WORST_CASE.contains(size)) {
+                WORST_CASE.add(size);
+                System.out.printf("%11d    %9d\n", len, size);
+            }
+        }
+    }
+    
+    private static void setBound(long len) {
+    	minRun = minRunLength(len);
+    }
+
+    private static int minRunLength(long n) {
+        assert n >= 0;
+        int r = 0;      // Becomes 1 if any 1 bits are shifted off
+        while (n >= MIN_MERGE) {
+            r |= (n & 1);
+            n >>= 1;
+        }
+        return (int)n + r;
+    }
+    
+    private static long first(long total) {
+    	if(    (8*minRun+9 <= total)
+    		|| (5*minRun+5 <= total && total <= 8*minRun+1)
+    		|| (3*minRun+3 <= total && total <= 4*minRun+1)) {
+    		return minRun+1;
+    	}
+    	while(total >= 2*minRun+1)
+    		total=total/2+1;
+    	return total;
+    }
+    
+    public static int JDKWorstCase(long length) {
+        setBound(length);
+        int stackSize=0;
+    	long runningTotal=0, curr=minRun+4, prev=minRun;
+    	
+    	while(runningTotal+curr+prev <= length) {
+            runningTotal += prev + curr;
+            stackSize +=2;
+            long diff = first(prev);
+    		prev = curr + diff + 1;
+    		curr += prev + 1;
+    	}
+    	
+    	if(runningTotal + prev <= length) {
+            runningTotal += prev;
+            stackSize++;
+    	}
+    	
+    	if(runningTotal < length)
+    	    stackSize++;
+    	return stackSize;
+    }
+
+    public static int correctWorstCase(int length) {
+        setBound(length);
+        int stackSize=1;
+        long curr = minRun, prev=0;
+        long runningTotal = length<minRun ? length : minRun;
+        
+        while(runningTotal+prev+curr+1 <= length) {
+            curr += prev+1;
+            prev=curr-prev-1;
+            runningTotal += curr;
+            stackSize++;
+        }
+        
+        if(runningTotal < length)
+            stackSize++;
+        return stackSize;
+    }
+}