You are given two integer arrays nums1
and nums2
. You are tasked to implement a data structure that supports queries of two types:
- Add a positive integer to an element of a given index in the array
nums2
. - Count the number of pairs
(i, j)
such thatnums1[i] + nums2[j]
equals a given value (0 <= i < nums1.length
and0 <= j < nums2.length
).
Implement the FindSumPairs
class:
FindSumPairs(int[] nums1, int[] nums2)
Initializes theFindSumPairs
object with two integer arraysnums1
andnums2
.void add(int index, int val)
Addsval
tonums2[index]
, i.e., applynums2[index] += val
.int count(int tot)
Returns the number of pairs(i, j)
such thatnums1[i] + nums2[j] == tot
.
Example 1:
Input ["FindSumPairs", "count", "add", "count", "count", "add", "add", "count"] [[[1, 1, 2, 2, 2, 3], [1, 4, 5, 2, 5, 4]], [7], [3, 2], [8], [4], [0, 1], [1, 1], [7]] Output [null, 8, null, 2, 1, null, null, 11] Explanation FindSumPairs findSumPairs = new FindSumPairs([1, 1, 2, 2, 2, 3], [1, 4, 5, 2, 5, 4]); findSumPairs.count(7); // return 8; pairs (2,2), (3,2), (4,2), (2,4), (3,4), (4,4) make 2 + 5 and pairs (5,1), (5,5) make 3 + 4 findSumPairs.add(3, 2); // now nums2 = [1,4,5,4,5,4
] findSumPairs.count(8); // return 2; pairs (5,2), (5,4) make 3 + 5 findSumPairs.count(4); // return 1; pair (5,0) makes 3 + 1 findSumPairs.add(0, 1); // now nums2 = [2
,4,5,4,5,4
] findSumPairs.add(1, 1); // now nums2 = [2
,5,5,4,5,4
] findSumPairs.count(7); // return 11; pairs (2,1), (2,2), (2,4), (3,1), (3,2), (3,4), (4,1), (4,2), (4,4) make 2 + 5 and pairs (5,3), (5,5) make 3 + 4
Constraints:
1 <= nums1.length <= 1000
1 <= nums2.length <= 105
1 <= nums1[i] <= 109
1 <= nums2[i] <= 105
0 <= index < nums2.length
1 <= val <= 105
1 <= tot <= 109
- At most
1000
calls are made toadd
andcount
each.
Companies:
Quora
Related Topics:
Hash Table, Design, Ordered Map
// OJ: https://leetcode.com/problems/finding-pairs-with-a-certain-sum/
// Author: github.com/lzl124631x
// Time:
// FindSumPairs: O(B)
// add: O(1)
// count: O(A)
// Space: O(A + B)
class FindSumPairs {
vector<int> A, B;
unordered_map<int, int> m;
public:
FindSumPairs(vector<int>& A, vector<int>& B): A(A), B(B) {
for (int n : B) m[n]++;
}
void add(int index, int val) {
int n = B[index];
if (--m[n] == 0) m.erase(n);
B[index] += val;
m[B[index]]++;
}
int count(int tot) {
int ans = 0;
for (int a : A) {
if (m.count(tot - a)) ans += m[tot - a];
}
return ans;
}
};