43 lines
1.0 KiB
C
43 lines
1.0 KiB
C
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//
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// Tomás Oliveira e Silva, AED, October 2021
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//
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// This program contains a flawed binary search implementation.
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// Use the gdb program to execute the binary_search() function
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// one line at a line and to examine the value of all relevant
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// variables to find where it goes wrong. (Do not put calls to
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// the printf function to discover what is wrong. In the context
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// of the present exercise that would be cheating.)
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//
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#include <stdio.h>
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int binary_search(int *a,int n,int d) {
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int lo = 0;
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int hi = n - 1;
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while(hi >= lo) {
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int middle = lo + (hi - lo) / 2;
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if(a[middle] == d)
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return middle; // found it
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if(a[middle] < d)
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lo = middle + 1;
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else
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hi = middle - 1;
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}
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return -1; // not found
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}
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int main(void) {
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int a[8] = { 1,3,8,11,18,19,23,27 };
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int i,d;
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for(d = 0;d <= 30;d++) {
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i = binary_search(a,8,d);
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if(i < 0)
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printf("%d not found\n",d);
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else
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printf("the index of %d is %d\n",d,i);
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}
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return 0;
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}
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