62 lines
1.9 KiB
Java
62 lines
1.9 KiB
Java
//给定四个包含整数的数组列表 A , B , C , D ,计算有多少个元组 (i, j, k, l) ，使得 A[i] + B[j] + C[k] + D[
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//l] = 0。
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//
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// 为了使问题简单化，所有的 A, B, C, D 具有相同的长度 N，且 0 ≤ N ≤ 500 。所有整数的范围在 -2²⁸ 到 2²⁸ - 1 之间，最
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//终结果不会超过 2³¹ - 1 。
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//
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// 例如:
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//
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//
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//输入:
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//A = [ 1, 2]
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//B = [-2,-1]
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//C = [-1, 2]
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//D = [ 0, 2]
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//
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//输出:
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//2
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//
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//解释:
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//两个元组如下:
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//1. (0, 0, 0, 1) -> A[0] + B[0] + C[0] + D[1] = 1 + (-2) + (-1) + 2 = 0
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//2. (1, 1, 0, 0) -> A[1] + B[1] + C[0] + D[0] = 2 + (-1) + (-1) + 0 = 0
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//
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// Related Topics 数组 哈希表 👍 408 👎 0
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package leetcode.editor.cn;
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import java.util.HashMap;
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import java.util.Map;
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//454:四数相加 II
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class FourSumIi {
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public static void main(String[] args) {
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//测试代码
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Solution solution = new FourSumIi().new Solution();
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}
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//力扣代码
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//leetcode submit region begin(Prohibit modification and deletion)
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class Solution {
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public int fourSumCount(int[] nums1, int[] nums2, int[] nums3, int[] nums4) {
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Map<Integer, Integer> map1 = new HashMap<>();
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Map<Integer, Integer> map2 = new HashMap<>();
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int size = nums1.length;
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for (int i = 0; i < size; i++) {
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for (int j = 0; j < size; j++) {
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map1.put(nums1[i] + nums2[j], map1.getOrDefault(nums1[i] + nums2[j], 0) + 1);
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map2.put(nums3[i] + nums4[j], map2.getOrDefault(nums3[i] + nums4[j], 0) + 1);
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}
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}
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int count = 0;
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for (int key : map1.keySet()) {
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if (map2.containsKey(-key)) {
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count += map1.get(key) * map2.get(-key);
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}
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}
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return count;
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}
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}
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//leetcode submit region end(Prohibit modification and deletion)
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} |