Arjun Suresh (talk | contribs) (→Explanation) |
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| + | <metadesc>C code to makes positive numbers appear after negative numbers in an array. </metadesc> | ||
| + | '''Given an array of positive and negative numbers, write a program to move the numbers such that all negative numbers appear before positive numbers | ||
| + | ''' | ||
| − | + | <!--<div class= "mw-collapsible mw-collapsed" id="mw-customcollapsible-code" >--> | |
| − | + | Complexity $\Theta(n)$ | |
| − | Complexity | ||
No. of swaps in the worst case = <math> \lfloor n/2 \rfloor</math> | No. of swaps in the worst case = <math> \lfloor n/2 \rfloor</math> | ||
| − | <syntaxhighlight lang="c"> | + | <syntaxhighlight lang="c" name="negative_positive"> |
| − | #include<stdio.h> | + | #include<stdio.h> |
int main() | int main() | ||
{ | { | ||
| − | int i,n,pi,ni, count = 0; | + | int i, n, pi, ni, count = 0; |
int a[1000]; | int a[1000]; | ||
printf("Enter size of array: "); | printf("Enter size of array: "); | ||
| Line 19: | Line 21: | ||
scanf("%d",&a[i]); | scanf("%d",&a[i]); | ||
} | } | ||
| − | ni =n-1; | + | ni = n-1; |
| + | /*Making ni point to the rightmost negative number*/ | ||
while(a[ni] >= 0) | while(a[ni] >= 0) | ||
ni--; | ni--; | ||
pi = 0; | pi = 0; | ||
| − | while(a[pi] <0) | + | /*Making pi point to the leftmost positive number*/ |
| + | while(a[pi] < 0) | ||
pi++; | pi++; | ||
| − | while(ni >pi) | + | /*Looping till either negative or positive numbers exhaust*/ |
| + | while(ni > pi) | ||
{ | { | ||
| + | /*Swapping a[ni] and a[pi]*/ | ||
int temp = a[pi]; | int temp = a[pi]; | ||
a[pi] = a[ni]; | a[pi] = a[ni]; | ||
a[ni] = temp; | a[ni] = temp; | ||
| + | /*Moving ni leftwards to the next negative number*/ | ||
while(a[ni] >= 0) | while(a[ni] >= 0) | ||
ni--; | ni--; | ||
| − | while(a[pi] <0) | + | /*Moving pi rightwards to the next positive number*/ |
| + | while(a[pi] < 0) | ||
pi++; | pi++; | ||
| Line 45: | Line 53: | ||
} | } | ||
</syntaxhighlight> | </syntaxhighlight> | ||
| + | |||
| + | ===Explanation=== | ||
| + | We are scanning the array from two ends. We scan for positive numbers from left and negative numbers from right and swaps them. As soon as one of them finishes, the algorithm stops. There are <math>n</math> elements, so there canʼt be more than <math>n/2</math> positive numbers and more than <math>n/2</math> negative numbers. | ||
| + | |||
| + | <!--<div class="mw-customtoggle-code " style="color:white;background-color:blue;width:60px"> Solution</div>--> | ||
| + | |||
| + | {{Template:FBD}} | ||
| + | |||
| + | |||
| + | |||
| + | |||
| + | [[Category:Placement Coding Questions from Arrays]] | ||
Given an array of positive and negative numbers, write a program to move the numbers such that all negative numbers appear before positive numbers
Complexity $\Theta(n)$
No. of swaps in the worst case = <math> \lfloor n/2 \rfloor</math>
<syntaxhighlight lang="c" name="negative_positive">
int main() {
GATECSE int i, n, pi, ni, count = 0;
int a[1000];
printf("Enter size of array: ");
scanf("%d",&n);
printf("Enter numbers of array\n");
for(i=0; i<n; i++)
{
scanf("%d",&a[i]);
}
ni = n-1;
/*Making ni point to the rightmost negative number*/
while(a[ni] >= 0)
ni--;
pi = 0;
/*Making pi point to the leftmost positive number*/
while(a[pi] < 0)
pi++;
/*Looping till either negative or positive numbers exhaust*/
while(ni > pi)
{
/*Swapping a[ni] and a[pi]*/
int temp = a[pi];
a[pi] = a[ni];
a[ni] = temp;
/*Moving ni leftwards to the next negative number*/
while(a[ni] >= 0)
ni--;
/*Moving pi rightwards to the next positive number*/
while(a[pi] < 0)
pi++;
}
for(i=0; i<n; i++)
{
printf("%d ", a[i]);
}
}
</syntaxhighlight>
We are scanning the array from two ends. We scan for positive numbers from left and negative numbers from right and swaps them. As soon as one of them finishes, the algorithm stops. There are <math>n</math> elements, so there canʼt be more than <math>n/2</math> positive numbers and more than <math>n/2</math> negative numbers.
Makes the positive numbers appear after the negative numbers in an array.
Complexity <math>\theta(n)</math>
No. of swaps in the worst case = <math> \lfloor n/2 \rfloor</math>
<syntaxhighlight lang="c">
int main() {
int i,n,pi,ni, count = 0;
int a[1000];
printf("Enter size of array: ");
scanf("%d",&n);
printf("Enter numbers of array\n");
for(i=0; i<n; i++)
{
scanf("%d",&a[i]);
}
ni =n-1;
while(a[ni] >= 0)
ni--;
pi = 0;
while(a[pi] <0)
pi++;
while(ni >pi)
{
int temp = a[pi];
a[pi] = a[ni];
a[ni] = temp;
while(a[ni] >= 0)
ni--;
while(a[pi] <0)
pi++;
}
for(i=0; i<n; i++)
{
printf("%d ", a[i]);
}
}
</syntaxhighlight>