179.c

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#defineN 12 /* max number of digits in 10-base integer */

intcompare(inta, intb) {
charstra[N] = { 0 };
charstrb[N] = { 0 };
sprintf(stra, "%d", a);
sprintf(strb, "%d", b);

charaplusb[N+N] = { 0 };
charbplusa[N+N] = { 0 };
strcpy(aplusb, stra);
strcat(aplusb, strb);

strcpy(bplusa, strb);
strcat(bplusa, stra);

returnstrcmp(aplusb, bplusa);
}

voidquicksort(int*nums, intleft, intright) {
if (left>right) return;

inti=left;
intj=right;
intpivot=nums[left];
while (i<j) {
while (i<j&&compare(nums[j], pivot) <= 0) j--;
nums[i] =nums[j];
while (i<j&&compare(nums[i], pivot) >= 0) i++;
nums[j] =nums[i];
 }
nums[i] =pivot;
quicksort(nums, left, i-1);
quicksort(nums, i+1, right);
}

char*largestNumber(int*nums, intnumsSize) {
quicksort(nums, 0, numsSize-1);
char*ans= (char*)calloc(numsSize*N, sizeof(char));
inti;
for (i=0; i<numsSize; i++) {
charbuf[N] = { 0 };
sprintf(buf, "%d", nums[i]);
strcat(ans, buf);
 }

/* skip leading zeros */
while (*ans=='0'&&*(ans+1) =='0') ans++;

returnans;
}

intmain() {
intnums0[] = { 3, 30, 34, 5, 9 };
printf("%s\n", largestNumber(nums0, sizeof(nums0) / sizeof(nums0[0])));

intnums1[] = { 0, 0 };
printf("%s\n", largestNumber(nums1, sizeof(nums1) / sizeof(nums1[0])));

return0;
}