http://www.codechef.com/problems/VOTERS

1. #include<stdio.h>
2. void mergesort(long long *ar,long long ,long long);
3. void merge(long long*ar,long long,long long,long long);
5. void mergesort(long long *ar,long long left,long long right)
6. {
7. long long mid=((left+right)/2);
8. if(left<right)
9. {
10. mergesort(ar,left,mid);
11. mergesort(ar,mid+1,right);
12. merge(ar,left,mid,right);
13. }
14. }
15. void merge(long long*ar,long long left,long long mid,long long right)
16. {
17. long long t[right-left+1];
18. long long pos=0;long long i;
19. long long lpos=left,rpos=mid+1;
20. while(lpos<=mid && rpos<=right)
21. {
22. if(ar[lpos]<ar[rpos])
23. {
24. t[pos++]=ar[lpos++];
25. }
26. else
27. {
28. t[pos++]=ar[rpos++];
29. }
30. }
31. while(lpos<=mid)
32. t[pos++]=ar[lpos++];
33. while(rpos<=right)
34. t[pos++]=ar[rpos++];
35. for(i=0;i<pos;i++)
36. ar[left+i]=t[i];
37. return ;
38. }
39. long long ar[1000000]={0},ans[1000000]={0};
40. int main()
41. {
42. long long n1,n2,n3,i,b=0,k=0,j;
43. long long ar1[50005],ar2[50005],ar3[50005];
44. scanf("%lld%lld%lld",&n1,&n2,&n3);
45. for(i=0;i<n1;i++)
46. scanf("%lld",&ar1[i]);
47. for(i=0;i<n2;i++)
48. scanf("%lld",&ar2[i]);
49. for(i=0;i<n3;i++)
50. scanf("%lld",&ar3[i]);
51. // first finding commom elements in first two arrays
52. i=0;j=0;
53. while(i<n1 && j<n2)
54. {
55. if(ar1[i]==ar2[j])
56. {
57. ar[b++]=ar1[i];
58. i++;j++;
59. }
60. else if(ar1[i]>ar2[j])
61. j++;
62. else
63. i++;
64. }
65. i=0;j=0;
66. while(i<n2 && j<n3)
67. {
68. if(ar2[i]==ar3[j])
69. {
70. ar[b++]=ar2[i];
71. i++;j++;
72. }
73. else if(ar2[i]>ar3[j])
74. j++;
75. else
76. i++;
77. }
78. i=0;j=0;
79. while(i<n1 && j<n3)
80. {
81. if(ar1[i]==ar3[j])
82. {
83. ar[b++]=ar1[i];
84. i++;j++;
85. }
86. else if(ar1[i]>ar3[j])
87. j++;
88. else
89. i++;
90. }
91. mergesort(ar,0,b-1);
92. if(ar[0]!=0)
93. ans[k++]=ar[0];
94. for(i=1;i<b;i++)
95. if(ar[i]!=ar[i-1])
96. ans[k++]=ar[i];
97. printf("%lld\n",k);
98. for(i=0;i<k;i++)
99. printf("%lld\n",ans[i]);
100. return 0;
101. }