Remove All Adjacent Duplicates In String

char * removeDuplicates(char * s){
    char * stack = calloc(1,strlen(s)+1);
    int top = -1;
    char c;
    while((c=*s++)!= '\0') {
        if (top == -1) {
            stack[++top] = c;
            
        } else if (stack[top] == c) {
            --top;
        } else {
            stack[++top] = c;
        }
    }
    stack[++top]='\0';
    return stack;
}