Question

Here is my code:when my input for input for array is 10001 .then also it is entering in else block for input[1]=0,where as i have put condition in outer if that if(input[j]==1).can any body tell me why it is happening?

#include<stdio.h>
int main()
{
        unsigned int tcase=0,build=0,i=0,j=0,k=0,count=0;
        unsigned int input[1000];
        scanf("%d",&tcase);
        while(tcase--)
        {
                scanf("%d",&build);
                for(i=0;i<build;i++)
                        scanf("%d",&input[i]);

                for(j=0;j<build;j++)
                {
                        if(input[j]==1)
                        {
                                if(j==0)
                                {       input[j+1]=1;

                                        printf("fddf");
                                }
                                else if(j==(build-1))
                                {
                                        input[j-1]=1;

                                        printf("Gfgf");
                                }
                                else
                                {
                                        input[j+1]=1;
                                        input[j-1]=1;
                                        printf("awGfgf");
                                }
                        }
                }
                for(k=0;k<build;k++)

               {
                        if(input[k]==0)
                                ++count;
                }
                printf("%d\n",count);
        }
        return 0;
}

Answer 1

I will answer your question based your comment to Eric J’s answer:

J.no u got it wrong by i/p 10001 i mean for input[0]=1,input[1]=0 and so on... so it only occupies 5 array spaces

The gist of the answer is that the first input you are entering as 1 which causes the condition to succeed first time. Later on in each iteration, you keep changing the values of your input array which causes subsequent iterations to enter into the condition.

As you mentioned your input is

input[0] = 1
input[1] = 0
input[2] = 0
input[3] = 0
input[4] = 1

Now, see the behavior in the below code:

for(j=0;j< build;j++)
{
    if(input[j]==1) /* First for input[0], this condition succeeds */
    {
         if(j==0)
         {
            input[j+1]=1; /* This line changes input[1] to 1, so next time in the loop the condition if(input[j] == 1 will succeed */
            printf("fddf");
         }
         else if(j==(build-1)) /* This condition will cause input[4] to be set to 1 and will cause if(input[j] == 1) to succeed for the last iteration of the loop */
         {
           input[j-1]=1;

           printf("Gfgf");
         }
        else /** This condition will cause input[2] & input[3] to be set to 1 and will again cause if(input[j] == 1) to succeed in successive loop iterations **/
        {
           input[j+1]=1;
           input[j-1]=1;
           printf("awGfgf");
        }
    }
  }