Careercup - Microsoft面试题 - 5684901156225024

2014-05-10 23:45

题目链接

原题：

Arrange the numbers in an array in alternating order. 
For example if the array is [a1, a2, a3, a4.. ]arrange the array such that b1<=b2>=b3<=b4 and so on. 
Sampe Input: 3 5 7 8 4 9 
Sample Output: 3 < 5 > 4 < 8 >7 < 9

题目：给定一个数组，请调整元素顺序，使得数组满足a <= b >= c <= d ...这样的交替单调性。

解法：之前也有类似题目，不过那一题要求严格的大于和小于。如果是大于等于和小于等于的话，可以保证在O(n)时间内完成算法。只要按顺序调整相邻元素就可以达到题目要求了。

代码：

// http://www.careercup.com/question?id=5684901156225024
#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

class Solution {
public:
    void arrangeArray(vector<int> &v) {
        int n;
        int i;
        
        n = (int)v.size();
        if (n < 2) {
            return;
        }
        
        int flag = 0;
        for (i = 0; i < n - 1; ++i) {
            if (flag ? v[i] < v[i + 1] : v[i] > v[i + 1]) {
                myswap(v[i], v[i + 1]);
            }
            flag = !flag;
        }
    };
private:
    void myswap(int &x, int &y)
    {
        int tmp = x;
        x = y;
        y = tmp;
    }
};

int main()
{
    int n;
    int i;
    vector<int> v;
    Solution sol;
    
    while (cin >> n && n > 0) {
        v.resize(n);
        for (i = 0; i < n; ++i) {
            cin >> v[i];
        }
        sol.arrangeArray(v);
        
        for (i = 0; i < n; ++i) {
            cout << v[i];
            cout << (i == n - 1 ? '\n' : ' ');
        }
        
        v.clear();
    }
    
    return 0;
}