Java | Leetcode Java题解之第454题四数相加II
题目:
题解:
class Solution {
public int fourSumCount(int[] A, int[] B, int[] C, int[] D) {
Map<Integer, Integer> countAB = new HashMap<Integer, Integer>();
for (int u : A) {
for (int v : B) {
countAB.put(u + v, countAB.getOrDefault(u + v, 0) + 1);
}
}
int ans = 0;
for (int u : C) {
for (int v : D) {
if (countAB.containsKey(-u - v)) {
ans += countAB.get(-u - v);
}
}
}
return ans;
}
}
原文地址:https://blog.csdn.net/m0_57195758/article/details/142698830
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