[003] largest_subarray_with_equal_1&0

[Description] Given an array with only ‘1‘ and ‘0‘, find a largest length sub-array which contains equal number of ‘1‘ and ‘0‘. Return the largest number.

e.g. arr[] = {1,0,1,0,0,0,1,1,0,1,1,0,1,1,1,0,0,1,1,1,0,1,0,1,1}

　　return : 16

[Thought] Preprocess this array by add 1/-1 to arr[i] while arr[i] is 1/0; find the last position of ‘0‘ as ‘largest1‘; find the farther distance of the same number as ‘largest2‘; return the larger one of ‘largest1‘ and ‘largest2‘.　　O(n^2)

[Implementation] C code:

 1 #include<stdio.h>
 2
 3 int largestSubarray(int str[],int size)
 4 {
 5         int largest=0;
 6         int i,j;
 7         str[0]?(str[0]=1):(str[0]=-1);
 8         // preprocess.
 9         for(i=1;i<size;i++)
10         {
11                 str[i]?(str[i]=str[i-1]+1):(str[i]=str[i-1]-1);
12         }
13         // find the last 0‘s position, and find the farther distance of the same numbers.
14         for(i=0;i<size;i++)
15         {
16                 // find the last 0‘s position.
17                 if(0 == str[i] && (i+1)>largest)
18                 {
19                         largest=i+1;
20 //                      printf("0:%d\n",largest);
21                 }
22                 // find the farther distance of the same numbers.
23                 for(j=0;j<i;j++)
24                 {
25                         if(str[i] == str[j] && (i-j)>largest)
26                         {
27                                 largest=i-j;
28 //                              printf("other:%d\n",largest);
29                                 break;
30                         }
31                 }
32         }
33         return largest;
34 }
35
36 int main()
37 {
38         int str[]={1,0,1,0,0,0,1,1,0,1,1,0,1,1,1,0,0,1,1,1,0,1,0,1,1};
39         int size=sizeof(str)/sizeof(str[0]);
40         int i;
41
42         printf("Initianl Sequence which size is %d :\n",size);
43         for(i=0;i<size;i++)
44         {
45                 printf("%d, ",str[i]);
46         }
47         printf("\nlargest:%d\n",largestSubarray(str,size));
48 }