Finding common characters in two strings

Question

I am coding for the problem in which we got to count the number of common characters in two strings. Main part of the count goes like this

for(i=0; i < st         


        

Answer 1

Following code traverses each sting only once. So the complexity is O(n). One of the assumptions is that the upper and lower cases are considered same.

 #include

int main() {
    char a[] = "Hello world";
    char b[] = "woowrd";
    int x[26] = {0};
    int i;
    int index;

    for (i = 0; a[i] != '\0'; i++) {
        index = a[i] - 'a';
        if (index > 26) {
            //capital char
            index = a[i] - 'A';
        }
        x[index]++;
    }

    for (i = 0; b[i] != '\0'; i++) {
        index = b[i] - 'a';
        if (index > 26) {
            //capital char
            index = b[i] - 'A';
        }

        if (x[index] > 0)
            x[index] = -1;
    }

    printf("Common characters in '%s' and '%s' are ", a, b);
    for (i = 0; i < 26; i++) {
        if (x[i] < 0)
            printf("%c", 'a'+i);
    }
    printf("\n");
}