Largest Number

int cmp(const void * a, const void * b){
	char * str1 = *(char**)a;
	char * str2 = *(char**)b;
	static buffer1[24] = { 0 };
	static buffer2[24] = { 0 };

	buffer1[0] = buffer2[0] = 0;

	strcat(buffer1, str1);
	strcat(buffer1, str2);
	strcat(buffer2, str2);
	strcat(buffer2, str1);
	return strcmp(buffer1, buffer2);
}
void printStrArr(char ** as, int num){
	for (int i = 0; i < num; ++i)
		printf("%s\n", as[i]);
}
char* largestNumber(int* nums, int numsSize) {
	if (numsSize<1) return NULL;
	char ** numstring = malloc(sizeof(char*)* numsSize);
	for (int i = 0; i < numsSize; ++i){
		char * s = malloc(sizeof(char)* 12);
		sprintf(s, "%d", nums[i]);
		numstring[i] = s;
	}
	//cmp(numstring[0], numstring[1]);
//	printStrArr(numstring, numsSize);
	qsort(numstring, numsSize, sizeof(char*), cmp);
//	printStrArr(numstring, numsSize);
	// cat all string
	char * buffer = malloc(sizeof(char) * 1280);
	buffer[0] = 0;

	for (int i = (numsSize - 1); i >= 0; --i){
		strcat(buffer, numstring[i]);
		free(numstring[i]);
	}
    // all zeros
    if(buffer[0] == '0')
        buffer[1] = 0;
	return buffer;
}