gistfile1.c

#include <stdio.h> 

static const int SIZE = 1000000;

int rank(int key, int arr[]);

int main(int argc, char *argv[]) {
        
        int array[SIZE];
        
        FILE *firstFile = NULL;
        if ((firstFile = fopen("largeW.txt", "r")) == NULL) {
            return 1;
        }

        int num;
        int count = 0;
        while (fscanf(firstFile, "%d", &num) > 0) {
            array[count] = num;
            count++;
        }
        
        FILE *secondFile = NULL;
        if ((secondFile = fopen("largeT.txt", "r")) == NULL) {
            return -2;
        }

        int value;
        while (fscanf(secondFile, "%d", &value) > 0) {
            if (rank(value, array) == -1){
                printf("Key %d\n", value);
            }
        }
        fclose(secondFile);
        fclose(firstFile);
    return 0;
}

int rank(int key, int arr[]) {
    int lo = 0;
    int hi = SIZE - 1;
    
    while (lo <= hi) {
        int mid = lo + (hi - lo) / 2;
        if (key < arr[mid]) hi = mid - 1;
        else if (key > arr[mid]) lo = mid + 1;
        else return mid;
    }
    
    return -1;
}