#include "stdio.h"

#define N 10 

int main(){
 char array[N]={"abcd"};
 int i;

 for (i=0; i<N; i++){
  printf("%c ", array[i]);
 }

// printf("last=%ceee",array[N-1]);
 return 0;
}

// 2 dimension array
#include "stdio.h"

#define N 10
#define P 3

int main(){
 char array[P][N]={"john", "mary", "jack"};
 int i;

 for (i=0; i<P; i++){
  printf("%s ", array[i]);
 }

 printf("\n");
 return 0;
}


// read file in
#include "stdio.h"
#include "stdlib.h"

#define N 3

int main(){
 FILE *fh;
 int i;
 int arr[N];

 fh = fopen("foo.txt", "r");
 if (fh == NULL){
  printf("Error Reading File\n");
  exit (0);
 }

 for (i=0; i<N; i++){ fscanf(fh, "%d,", &arr[i]); }
 for (i=0; i<N; i++){ printf(    "%d ",  arr[i]); }

 return 0;
}


/*
foo.txt
--
john 80
mary 90
tom 70
*/
// find max 
#include "stdio.h"
#include "stdlib.h"

#define P 3
#define N 9

int main(){
 FILE *fh;
 int i;
 char acc[P][N];
 int score[P];
 int max, max_i;

 fh = fopen("foo.txt", "r");
 if (fh == NULL){
  printf("Error Reading File\n");
  exit (0);
 }

 for (i=0; i<P; i++){
  fscanf(fh, "%s %d", acc[i], &score[i]);
 }
 max = score[0];
 max_i=0;

 for (i=0; i<P; i++){
   if (score[i] > max){
    max=score[i];
    max_i=i;
   }
 }

 printf("index=%d name=%s score=%d\n", max_i, acc[max_i], max);
 return 0;
}


// pointer
#include "stdio.h"
#include "stdlib.h"

int main(){
 int x = 1, y = 2, z[10];

 int *ip;       // ip is a pointer to int
 ip = &x;       // ip now points to x
 y = *ip;       // y is now 1
 *ip = 0;       // x is now 0
 ip = &z[0];    // ip now points to z[0]

 return 0;
}

//swap
#include "stdio.h"
#include "stdlib.h"
#define N 2

void swap(int *,int *);

int main(){
 int arr[N]={1,2};

 printf("%d %d\n", arr[0], arr[1]);
 swap(&arr[0], &arr[1]);
 printf("%d %d\n", arr[0], arr[1]);

 return 0;
}

void swap(int *px, int *py) {
 int temp;

 temp = *px;
 *px = *py;
 *py = temp;
}

//length
#include "stdio.h"
#include "stdlib.h"

int my_strlen(char *);

int main(){
 char arr[]="john";

 printf("size of arr = %d\n", my_strlen(arr));
 return 0;
}

int my_strlen(char *s){
 int n;

 for (n = 0; *s != '\0'; s++){
  n++;
 }

 return n;
}

// strlen version2
#include "stdio.h"
#include "stdlib.h"

int my_strlen(char *);

int main(){
 char arr[]="john";

 printf("size of arr = %d\n", my_strlen(arr));
 return 0;
}

int my_strlen(char *s){
 char *p=s;

 while (*p != '\0'){
  p++;
 }

 return p-s;
}