面试宝典-面试题3.1：数组中的重复数字

 1 #include"iostream"
 2 #include"stdio.h"
 3 #include"string.h"
 4 using namespace std;
 5 
 6 const int MAXN=100000;
 7 
 8 int num[MAXN];
 9 int visited[MAXN];
10 
11 int GetRepeat1(int n)
12 {
13     int i;
14     for(i=0;i<n;i++)
15     {
16         if(!visited[num[i]])
17             visited[num[i]]=1;
18         else
19             return num[i];
20     }
21     return -1;
22 }
23 
24 int GetRepeat2(int n)
25 {
26     int i=0,temp;
27     while(i<n)
28     {
29         if(num[i]==i) i++;
30         else if(num[i]==num[num[i]]) return num[i];
31         else
32         {
33             temp=num[i];
34             num[i]=num[temp];
35             num[temp]=temp;
36         }
37     }
38     return -1;
39 }
40 
41 int main()
42 {
43     int n;
44     while(scanf("%d",&n)==1)
45     {
46         //可加入判断，判断n是否小于1
47         for(int i=0;i<n;i++)
48             cin>>num[i];//可加入判断，判断输入的数是否在0~n-1之间
49         memset(visited,0,sizeof(visited));
50         int res=GetRepeat1(n);
51         if(res!=-1)
52             cout<<"test for function1-the one of repeat number is: "<<res<<endl;
53         else
54             cout<<"no repeat number"<<endl;
55         res=GetRepeat2(n);
56         if(res!=-1)
57             cout<<"test for function2-the one of repeat number is: "<<res<<endl;
58         else
59             cout<<"no repeat number"<<endl;
60     }
61 }