int arr[5] = { 0 };
int main() { int n = 0, q = 0, x = 0; int a = 0; int r = 0, l = 0; int i = 4;
n = 5;
r = (n - 1);
q = 10;
for (int j = (n - 1); j>(-1); j--)
{
arr[j] = 10 + 10 * i;
printf("arr[%d] = %d\n", j, arr[j]);
i--;
}
for (int k = 0; k<q; k++)
{
x = 10 + 10 * k;
printf("x=%d ", x);
while (r >= l)
{
int m = ((l + r) / 2);
if (x == arr[m])
{
a = 1;
break;
}
if (x < arr[m])
r = m - 1;
else
l = m + 1;
}
if (a == 1)
printf("YES\n");
else
printf("NO\n");
a = 0;
}
return 0;
}
If you use the following source code, you will get NO from 30Can I know the reason?
binary search
The second for loop letter r and l are not initialized.
#include <stdio.h>
int arr[5] = { 0 };
int main() {
int n = 5, q = 10;
int a = 0;
for(int i=0; i<n; i++)
{
arr[i] = 10 + 10 * i;
}
for (int k = 0; k < q; k++)
{
int = n-1, l = 0; // initialize r, l for statement first.
int x = 10 + 10 * k;
printf("x=%d ", x);
while (r >= l)
{
int m = ((l + r) / 2);
if (x == arr[m])
{
a = 1;
break;
}
if (x < arr[m])
r = m;
else
l = m + 1;
}
if (a == 1)
printf("YES\n");
else
printf("NO\n");
a = 0;
}
return 0;
}
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