a c program to check palindrome

#include<stdio.h>
#include<conio.h>
#include<math.h>
#include<string.h>
int main ()
{char str1[100];
char str2[100];
printf("entr a srting   \n");
gets(str1);

strcpy(str2,str1);
strrev(str2);
if(strcmp(str1,str2)==0)
printf("it is a palindrome");
else
printf("not a palindrome");





getch();
return 0;
}

C program code to convert decimal to hexadecimal

#include<stdio.h>
#include<conio.h>
#include<math.h>
void dtoh(int d);
main()
{

int d;
printf("Enter a no. in decimal system:- ");
scanf("%d",&d);
dtoh(d);

getch();
}

void dtoh(int d)
{
int b,c=0,a[5],i=0;
b=d;
while (b>15)
{
a[i]=b%16;
b=b/16;
i++;
c++;
}
a[i]=b;
printf("Its hexadecimal equivalent is ");
for (i=c;i>=0;--i)
{
if (a[i]==10)
printf("A");
else if (a[i]==11)
printf("B");
else if (a[i]==12)
printf("C");
else if (a[i]==13)
printf("D");
else if (a[i]==14)
printf("E");
else if (a[i]==15)
printf("F");
else
printf("%d",a[i]);
}
return o;
}

TO COUNT NUMBER OF WORDS IN A SENTENCE

#include<stdio.h>
#include<conio.h>
#include<math.h>
#include<string.h>
int main ()
{char str1[100];
int i,x,c;
gets(str1);
c=0;
for(i=0;str1[i]!='\0';++i)
{
if(str1[i]==' ')
++c;
}


x=c+1;



printf("no of word is %d",x);
getch();
return 0;
}

TO FIND THE DETERMINANT OF THE MATRIX

#include<stdio.h>
#include<math.h>
float detrm(float[][],float);
void cofact(float[][],float);
void trans(float[][],float[][],float);
main()
{
float a[25][25],k,d;
int i,j;
printf("ENTER THE ORDER OF THE MATRIX:\n");
scanf("%f",&k);
printf("ENTER THE ELEMENTS OF THE MATRIX:\n");
for(i=0;i<k;i++)
{
for(j=0;j<k;j++)
{
scanf("%f",&a[i][j]);
}
}
d=detrm(a,k);
printf("THE DETERMINANT IS=%f",d);
if(d==0)
printf("\nMATRIX IS NOT INVERSIBLE\n");
else
cofact(a,k);
}
/******************FUNCTION TO FIND THE DETERMINANT OF THE MATRIX************************/


float detrm(float a[25][25],float k)
{
float s=1,det=0,b[25][25];
int i,j,m,n,c;
if(k==1)
{
return(a[0][0]);
}
else
{
det=0;
for(c=0;c<k;c++)
{
m=0;
n=0;
for(i=0;i<k;i++)
{
for(j=0;j<k;j++)
{
b[i][j]=0;
if(i!=0&&j!=c)
{
b[m][n]=a[i][j];
if(n<(k-2))
n++;
else
{
n=0;
m++;
}
}
}
}
det=det+s*(a[0][c]*detrm(b,k-1));
s=-1*s;
}
}
return(det);
}



/*******************FUNCTION TO FIND COFACTOR*********************************/


void cofact(float num[25][25],float f)
{
float b[25][25],fac[25][25];
int p,q,m,n,i,j;
for(q=0;q<f;q++)
{
for(p=0;p<f;p++)
{
m=0;
n=0;
for(i=0;i<f;i++)
{
for(j=0;j<f;j++)
{
b[i][j]=0;
if(i!=q&&j!=p)
{
b[m][n]=num[i][j];
if(n<(f-2))
n++;
else
{
n=0;
m++;
}
}
}
}
fac[q][p]=pow(-1,q+p)*detrm(b,f-1);
}
}
trans(num,fac,f);
}


/*************FUNCTION TO FIND TRANSPOSE AND INVERSE OF A MATRIX**************************/



void trans(float num[25][25],float fac[25][25],float r)

{
int i,j;
float b[25][25],inv[25][25],d;
for(i=0;i<r;i++)
{
for(j=0;j<r;j++)
{
b[i][j]=fac[j][i];
}
}

d=detrm(num,r);
inv[i][j]=0;
for(i=0;i<r;i++)
{
for(j=0;j<r;j++)
{
inv[i][j]=b[i][j]/d;
}
}

printf("\nTHE INVERSE OF THE MATRIX:\n");
for(i=0;i<r;i++)
{
for(j=0;j<r;j++)
{
printf("\t%f",inv[i][j]);
}
printf("\n");
}
}

solution of balagurusamy of chapter 8.15

#include<stdio.h>

int main()
{
    int i,j;
    char str[]="123456789",*p;
    p=str;
    for(i=0;i<5;i++)
    {
        printf("%5.*s",i+1,p+i);
        for(j=i-1;j>=0;j--)
            printf("%c",*(p+i+j));
        printf("\n");
    }
    return 0;
}