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leetcode 18

思路

参考三数之和，四数之和在三数之和外再套一层循环，然后里面内容跟三数之和一致，去重逻辑也一致

实现

var fourSum = function (nums, target) {nums.sort((a, b) => a - b);let result = [];for (let i = 0; i < nums.length - 3; i++) {if (i > 0 && nums[i] === nums[i - 1]) continue;for (let j = i + 1; j < nums.length - 2; j++) {if (j > i + 1 && nums[j] === nums[j - 1]) continue;let left = j + 1, right = nums.length - 1;while (left < right) {if (left > j + 1 && nums[left] === nums[left - 1]) {left++;continue;}if (right > nums.length - 1 && nums[right] === nums[right - 1]) {right--;continue;}const sum = nums[i] + nums[j] + nums[left] + nums[right];if (sum === target) {result.push([nums[i], nums[j], nums[left], nums[right]]);left++;} else if (sum < target) {left++;} else {right--;}}}}return result;
};