#include <stdio.h>
 #define ITEMS 5
 #define CHOICES 3

 int find(int value, int list[], int size) {
     int i = 0;

     while (i < size && value != list[i]) {
         printf("%04d ", list[i]);
         i++;
     }
     putchar('\n');

     return i;
 }

 void display(int list[], int n) {
     int i;

     for (i = 0; i < n; i++)
         printf("%04d%c ", list[i], i < n - 1 ? ',' : ' ');
     putchar('\n');
 }


 int main(void) {
     int i, j, n = 0;
     int subject[ITEMS] = {100, 120, 110, 130, 140};
     int choice[CHOICES] = {140, 200, 120}, selected[ITEMS];

     printf("Subjects : ");
     display(subject, ITEMS);
     printf("Choices  : ");
     display(choice, CHOICES);

     for (i = 0; i < CHOICES; i++) {
         j = find(choice[i], subject, ITEMS);
         if (j >= 0 && j < ITEMS) {
             selected[n] = choice[i];
             n++;
         }
     }

     printf("Selected : ");
     display(selected, n);

     return 0;
 }

这边的一种练习，叫walkthrough,看代码，写出运行结果。

谢谢指点。