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83 lines
1.8 KiB
C++
83 lines
1.8 KiB
C++
#include <Core/Core.h>
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using namespace Upp;
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const int N = 1000000;
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// M. D. MCILROY
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// Appendix. An adversary for
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// qsort
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#include <stdlib.h>
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int *val; /* item values */
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int ncmp; /* number of comparisons */
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int nsolid; /* number of solid items */
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int candidate; /* pivot candidate */
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int gas; /* gas value */
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#define freeze(x) val[x] = nsolid++
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int cmp(const void *px, const void *py) /* per C standard */
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{
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const int x = *(const int*)px;
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const int y = *(const int*)py;
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ncmp++;
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if(val[x]==gas && val[y]==gas)
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if(x == candidate)
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freeze(x);
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else
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freeze(y);
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if(val[x] == gas)
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candidate = x;
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else if(val[y] == gas)
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candidate = y;
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return val[x] - val[y]; /* only the sign matters */
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}
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int antiqsort(int n, int *a)
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{
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int i;
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int *ptr = (int *)malloc(n*sizeof(*ptr));
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val = a;
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gas = n - 1;
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nsolid = ncmp = candidate = 0;
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for(i=0; i<n; i++) {
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ptr[i] = i;
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val[i] = gas;
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}
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qsort(ptr, n, sizeof(*ptr), cmp);
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free(ptr);
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return ncmp;
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}
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CONSOLE_APP_MAIN
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{
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StdLogSetup(LOG_COUT|LOG_FILE);
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for(int n = -1; n <= 10; n++) {
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Vector<String> h;
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for(int i = 0; i < N; i++)
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if(n < 0)
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h.Add(AsString(N - i));
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else
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if(n)
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h.Add(AsString(Random(n)));
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else
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h.Add(AsString(Random()));
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TimeStop tm;
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Sort(h);
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double t = tm.Seconds();
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RLOG(n << " " << t << " s");
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}
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Buffer<int> aq(N);
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RLOG("Generating antiqsort");
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antiqsort(N, aq);
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Vector<String> h;
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for(int i = 0; i < N; i++)
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h.Add(AsString(aq[i]));
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RLOG("Now sorting");
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TimeStop tm;
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Sort(h);
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double t = tm.Seconds();
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RLOG("antiqsort " << t << " s");
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}
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