squeeze.c

#include <stdio.h>

// remove all characters in string[] that occur in remove[]
void squeeze(char string[], char remove[]) {
    int i, x;

    for (i = x = 0; string[i] != '\0'; i++) {
        int removeChar = 0;

        for (int j = 0; remove[j] != '\0'; j++) {
            if (string[i] == remove[j]) {
                removeChar = 1;
                break;
            }
        }

        if (!removeChar) {
            string[x++] = string[i];
        }
    }

    string[x] = '\0';
}

int main() {
    char string[] = "Something about a fox";

    squeeze(string, "something a");

    printf("%s\n", string);
}