Topic Connection

http://acm.hdu.edu.cn/showproblem.php?pid=2095

Hdu 2095 Find Your Present (2) Description

In the New year party, everybody'll get a "special present". Now it's your turn to get your special present, a lot of presents now putting on the desk, and only one of the them would be yo Urs. Each present have a card number on it, and your present ' s card number would be the one that different from all the others, a nd you can assume this only one number appear odd times. For example, there is 5 present, and their card numbers are 1, 2, 3, 2, 1.so your present would be is the one with the card n Umber of 3, because 3 is the number, which different from all the others.

Input

The input file is consist of several cases.

Each case would be presented by an integer n (1<=n<1000000, and n are odd) at first. Following that, n positive integers would be given in a line, all integers would smaller than 2^31. These numbers indicate the card numbers of the PRESENTS.N = 0 ends the input.

Output

For each case, output an integer in a line, which is the card number of your present.

Sample Input

5

1 1 3) 2 2

3

1 2 1

0

Sample Output

3

2

Hash

#include <algorithm> #include <iostream> #include <cstdlib> #include <cstring> #include < cstdio> #include <vector> #include <map>using std::map;using std::min;using std::find;using std::p air; Using std::vector;using std::multimap; #define PB (E) push_back (e) #define SZ (c) (int) (c). Size () #define MP (A, b) make_pair (A, B) #define ALL (c) (c). Begin (), (c). End () #define ITER (c) __typeof ((c). Begin ()) #define CLS (arr, Val) memset (arr, Val, si Zeof (arr)) #define Cpresent (C, E) (Find (All (c), (e))! = (c). End ()) #define REP (i, n) for (int i = 0; i < (int) n; i++) #defi NE tr (c, I) for (ITER (c) i = (c). Begin (); I! = (c). end (); ++i) const int N = 1000007;const int INF = 0x3f3f3f3f;int Arr[n];s truct hash_set {int tot, num[n], head[n], next[n]; inline void init (int n) {tot = 0; Rep (i, n + 1) head[i] =-1; } inline void Insert (int val) {int u = val% N; Num[tot] = u, Next[tot] = Head[u], head[u] = tot++; } inline bool Find (int val) { int tot = 0, u = val% N; for (int i = head[u]; ~i; i = Next[i]) {if (num[i] = = val) tot++; if (Tot >= 2) return true; } return false; }}hash;int Main () {#ifdef LOCAL freopen ("In.txt", "R", stdin); Freopen ("OUT.txt", "w+", stdout); #endif int n; while (~SCANF ("%d", &n), N) {hash.init (n); Rep (i, N) {scanf ("%d", &arr[i]); Hash.insert (Arr[i]); } Rep (I, N) {if (!hash.find (Arr[i])) {printf ("%d\n", Arr[i]); Break }}} return 0;}

stl

#include <algorithm> #include <iostream> #include <cstdlib> #include <cstring> #include < cstdio> #include <vector> #include <map>using std::map;using std::min;using std::find;using std::p air; Using std::vector;using std::multimap; #define PB (E) push_back (e) #define SZ (c) (int) (c). Size () #define MP (A, b) make_pair (A, B) #define ALL (c) (c). Begin (), (c). End () #define ITER (c) __typeof ((c). Begin ()) #define CLS (arr, Val) memset (arr, Val, si Zeof (arr)) #define Cpresent (C, E) (Find (All (c), (e))! = (c). End ()) #define REP (i, n) for (int i = 0; i < (int) n; i++) #defi NE tr (c, I) for (ITER (c) i = (c). Begin (); I! = (c). end (); ++i) const int N = 1000007;const int INF = 0x3f3f3f3f;map<int, Int> A;map<int, Int>::iterator it;int main () {#ifdef LOCAL freopen ("In.txt", "R", stdin); Freopen ("OUT.txt", "w+", stdout); #endif int n, v; while (~SCANF ("%d", &n), N) {Rep (i, N) {scanf ("%d", &v); a[v]++; } for (it = A.begin(); It! = A.end (); ++it) {if (It->second = = 1) {printf ("%d\n", It->first); Break }} a.clear (); } return 0;}

Hdu 2095 Find Your present (2)