7-2日刷题

3 Sum Closest

    public int threeSumClosest(int[] numbers ,int target) {
        // write your code here
        int minEr = Integer.MAX_VALUE;
        int ret = 0;
        Arrays.sort(numbers);
        for (int i = 1; i < numbers.length - 1; ++i) {
            int p1 = 0, p2 = numbers.length - 1;
            while (p1 < i && p2 > i) {
                int s1 = numbers[p1] + numbers[p2] + numbers[i] - target;
                if (Math.abs(s1) < minEr) {
                    minEr = Math.abs(s1);
                    ret = numbers[p1] + numbers[p2] + numbers[i];
                }
                if (s1 > 0) {
                    --p2;
                } else if (s1 < 0) {
                    ++p1;
                } else {
                    return target;
                }
            }
        }
        return ret;
    }

 3 Sum

   public ArrayList<ArrayList<Integer>> threeSum(int[] numbers) {
        // write your code here
        ArrayList<ArrayList<Integer>> ret = new ArrayList<ArrayList<Integer>>();
        Arrays.sort(numbers);
        ArrayList<String> mp = new ArrayList<>();
        for (int i = 1; i < numbers.length - 1; ++i) {
            int p1 = 0, p2 = numbers.length - 1;
            while (p1 < i && p2 > i) {
                int sum = numbers[i] + numbers[p1] + numbers[p2];
                if (sum > 0) {
                    --p2;
                } else if (sum < 0) {
                    ++p1;
                } else {
                    ArrayList<Integer> ad = new ArrayList<>();
                    String tag = numbers[p1] + "#" + numbers[i] + "#" + numbers[p2];
                    if (!mp.contains(tag)) {
                        ad.add(numbers[p1]);
                        ad.add(numbers[i]);
                        ad.add(numbers[p2]);
                        ret.add(ad);
                        mp.add(tag);
                    }
                    --p2;
                    ++p1;
                }
            }
        }
        return ret;
    }

 C++：

    vector<vector<int> > threeSum(vector<int> &nums) {
        // write your code here
        vector<vector<int> > result;
        sort(nums.begin(), nums.end());
        for (int i = 0; i < nums.size(); ++i) {
            if (i > 0 && nums[i] == nums[i - 1]) {
                continue;
            }
            int left = i + 1;
            int right = nums.size() - 1;
            while (left < right) {
                int sum = nums[i] + nums[left] + nums[right];
                if (sum < 0) {
                    ++left;
                } else if (sum > 0) {
                    --right;
                } else {
                    vector<int> triple;
                    triple.push_back(nums[i]);
                    triple.push_back(nums[left]);
                    triple.push_back(nums[right]);
                    result.push_back(triple);
                    ++left;
                    --right;
                    while (left < right && nums[left - 1] == nums[left]) {
                        ++left;
                    }
                    while (left < right && nums[right] == nums[right + 1]) {
                        ++right;
                    }
                }
            }
        }
        return result;
    }

Partition Array

这地方写了一年都没写对，得去练练怎么写快排了

    int partitionArray(vector<int> &nums, int k) {
        // write your code here
        int i = 0, j = nums.size() - 1;
        while (i <= j) {
            while (i <= j && nums[i] < k) ++i;
            while (i <= j && nums[j] >= k) --j;
            if (i <= j) {
                int tmp = nums[i];
                nums[i] = nums[j];
                nums[j] = tmp;
                ++i;
                --j;
            }
        }
        return i;
    }