18.4Sum

Posted 2021-02-18

鏍囩锛?a href='http://www.mamicode.com/so/1/sort' title='sort'>sort   solution   col   绛変簬   get   for   tor   3sum   tco   

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Given array nums = [1, 0, -1, 0, -2, 2], and target = 0.

A solution set is:
[
銆€[-1, 0, 0, 1],
銆€[-2, -1, 1, 2],
銆€[-2, 0, 0, 2]
]

 

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vector<vector<int>> fourSum(vector<int>& nums, int target) {
    vector<vector<int>> res;
    sort(nums.begin(), nums.end());
    int n = nums.size();
    for (int i = 0; i < n-3; i++) {
        if (i > 0 && nums[i] == nums[i - 1]) continue;
        for (int j = i + 1; j < n - 2; j++) {
            if (j > i + 1 && nums[j] == nums[j - 1]) continue;
            int l = j + 1, r = n - 1, remain = target - nums[i] - nums[j];
            while (l < r) {
                if (l > j+1 && nums[l] == nums[l - 1]) {
                    l++; continue;
                }
                if (nums[l] + nums[r] > remain) r--;
                else if (nums[l] + nums[r] < remain) l++;
                else res.push_back({ nums[i],nums[j],nums[l++],nums[r--] });
            }
        }
    }
    return res;
}