Java | Leetcode Java题解之第446题等差数列划分II-子序列
题目：
题解：
class Solution {
public int numberOfArithmeticSlices(int[] nums) {
int ans = 0;
int n = nums.length;
Map<Long, Integer>[] f = new Map[n];
for (int i = 0; i < n; ++i) {
f[i] = new HashMap<Long, Integer>();
}
for (int i = 0; i < n; ++i) {
for (int j = 0; j < i; ++j) {
long d = 1L * nums[i] - nums[j];
int cnt = f[j].getOrDefault(d, 0);
ans += cnt;
f[i].put(d, f[i].getOrDefault(d, 0) + cnt + 1);
}
}
return ans;
}
}