05 August 2008
Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), …, (an, bn) which makes sum of min(ai, bi) for all i from 1 to n as large as possible.
Example 1:
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Input: [1,4,3,2]
Output: 4
Explanation: n is 2, and the maximum sum of pairs is 4 = min(1, 2) + min(3, 4).
Note:
这道题要求把2n个元素的数组两两一对分成n个，然后找到每一对中较小的那个，加起来的和是最大的；使用greedy，将比较临近的两个数字排成一对，取其中较小值（如果把很小和很大的数字放在一起，去小的数字，那大的数字就不在结果中了）。具体做法是先排序然后隔一个数字取一下就行了。
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class Solution {
public int arrayPairSum(int[] nums) {
Arrays.sort(nums);
int result = 0;
for (int i = 0; i < nums.length; i += 2) {
result += nums[i];
}
return result;
}
}