1.sort 和  lower_bound 

例如     marble      https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1415

1 #include 
      
        2 #include 
       
         3 const  int  maxn = 10000; 4 using namespace std; 5 int main() 6 { 7     //freopen("in","r",stdin); 8     //freopen("out","w",stdout); 9     int n, x,j, Q, i, m[maxn],kase=0;10     while (scanf("%d%d", &n, &Q) == 2 && n)11     {12         for (i = 0; i < n; i++)13             scanf("%d", &m[i]);14         sort(m, m + n);15         printf("CASE# %d:\n",++kase);16         while (Q--)17         {18             scanf("%d", &x);19             int p = lower_bound(m, m + n, x) - m;20             if (m[p] == x)21                 printf("%d found at %d\n", x, p+1);22             else23                 printf("%d not found\n", x);24         }25     }26     return 0;27 }