LeetCode: 4Sum

跟3sum和3sum closest差不多

C++：

 1 class Solution {
 2  public:
 3      vector<vector<int> > fourSum(vector<int> &num, int target) {
 4          // Start typing your C/C++ solution below
 5          // DO NOT write int main() function
 6          vector<vector<int>> ret;
 7          if (num.size() < 4) return ret;
 8          sort(num.begin(), num.end());
 9          for (int i = 0; i < num.size()-3; i++) {
10              if (i > 0 && num[i] == num[i-1]) continue;
11              for (int j = i+1; j < num.size()-2; j++) {
12                  if (j > i+1 && num[j] == num[j-1]) continue;
13                  int end = num.size()-1;
14                  for (int beg = j+1; beg < end; beg++) {
15                      if (beg > j+1 && num[beg] == num[beg-1]) continue;
16                      int sum = num[i] + num[j] + num[beg] + num[end];
17                      if (sum == target) {
18                          vector<int> tmp;
19                          tmp.push_back(num[i]);
20                          tmp.push_back(num[j]);
21                          tmp.push_back(num[beg]);
22                          tmp.push_back(num[end]);
23                          ret.push_back(tmp);
24                      }
25                      else if (sum > target) end--, beg--;
26                  }
27              }
28          }
29          return ret;
30      }
31  };

java:

 1 public class Solution {
 2     public List<List<Integer>> fourSum(int[] nums, int target) {
 3         List<List<Integer>> ans = new ArrayList<List<Integer>>();
 4         Arrays.sort(nums);
 5         for (int i = 0; i < nums.length; i++) 
 6         {
 7             if (i > 0 && nums[i] == nums[i-1]) continue;
 8             for (int j = i+1; j < nums.length; j++)
 9             {
10                 if (j > i+1 && nums[j] == nums[j-1]) continue;
11                 int left = j+1;
12                 int right = nums.length-1;
13                 while (left < right)
14                 {
15                     if (left > j+1 && nums[left] == nums[left-1]) {
16                         left++;
17                         continue;
18                     }
19                     int sum = nums[i] + nums[j] + nums[left] + nums[right];
20                     if (sum == target) {
21                         List<Integer> tmp = new ArrayList<Integer>();
22                         tmp.add(nums[i]);
23                         tmp.add(nums[j]);
24                         tmp.add(nums[left]);
25                         tmp.add(nums[right]);
26                         ans.add(tmp);
27                         left++;
28                     }
29                     else if (sum < target) left++;
30                     else right--;
31                 }
32             }
33         }
34         return ans;
35     }
36 }

View Code

posted @ 2013-03-15 01:39 ying_vincent 阅读(179) 评论(0) 编辑收藏举报

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