Careercup - Facebook面试题 - 5435439490007040

2014-05-02 07:37

题目链接

原题：

// merge sorted arrays 'a' and 'b', each with 'length' elements,
// in-place into 'b' to form a sorted result. assume that 'b'
// has 2*length allocated space.
// e.g. a = [1, 3, 5], b = [2, 4, 6] => b = [1, 2, 3, 4, 5, 6] 

//how to do it without rearanging the b array

题目：有两个排好序的数组a[]和b[]，把a有序归并到b中去，保证b的空间充足。如何就地完成这个算法？

解法：从后往前归并就可以不用额外空间了。

代码：

 // http://www.careercup.com/question?id=5435439490007040
 #include <iostream>
 #include <vector>
 using namespace std;

 class Solution {
 public:
     void mergeTwoArray (vector<int> &a, vector<int> &b) {
         // merge a[] into b[].
         int na = (int)a.size();
         int nb = (int)b.size();

         b.resize(na + nb);

         int i, j, k;

         i = na - ;
         j = nb - ;
         k = na + nb - ;
         while (i >=  && j >= ) {
             b[k--] = a[i] > b[j] ? a[i--] : b[j--];
         }
         while (i >= ) {
             b[k--] = a[i--];
         }
     };
 };

 int main()
 {
     vector<int> a, b;
     int na, nb;
     int i;
     Solution sol;

     while (cin >> na >> nb && (na >  && nb > )) {
         a.resize(na);
         b.resize(nb);
         for (i = ; i < na; ++i) {
             cin >> a[i];
         }
         for (i = ; i < nb; ++i) {
             cin >> b[i];
         }
         sol.mergeTwoArray(a, b);
         nb = (int)b.size();
         for (i = ; i < nb; ++i) {
             i ? (cout << ' ', ) : ;
             cout << b[i];
         }
         cout << endl;

         a.clear();
         b.clear();
     }

     return ;
 }