tomatocream
ab80017903
- iterator.org: C++ iterator flashcard deck - questions.org: LeetCode question index (217, 242) - inbox.org: learning inbox with two-sum implementation and notes - sync-anki.sh: batch sync org files to Anki via emacsclient - AGENTS.md: conventions for AI agents working in this repo Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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1. two sum
class Solution {
public:
vector<int> twoSum(vector<int> &nums, int target) {
vector<pair<int, int>> rev;
// Fix 1 & 2: Loop over nums.size() and push nums[i]
for (int i = 0; i < nums.size(); i++) {
rev.push_back({nums[i], i});
}
std::sort(rev.begin(), rev.end());
for (int i = 0; i < rev.size(); i++) {
int want = target - rev[i].first;
// Fix 3: Pass the SORTED vector 'rev' to the search
int j = bs(rev, want, i + 1);
if (j >= 0) {
int a = rev[i].second;
int b = rev[j].second;
return vector<int>{min(a, b), max(a, b)};
}
}
return {};
}
// Updated to handle vector of pairs
using PairIter = vector<pair<int, int>>::iterator;
PairIter lower_bound(PairIter l, PairIter r, int target) {
while (l < r) {
PairIter mid = l + (r - l) / 2;
if (mid->first >= target) { // Access value via .first or ->first
r = mid;
} else {
l = mid + 1;
}
}
return l;
}
int bs(vector<pair<int, int>> &indexedNums, int target, int offset) {
auto it =
lower_bound(indexedNums.begin() + offset, indexedNums.end(), target);
if (it == indexedNums.end() || it->first != target) {
return -1;
}
return it - indexedNums.begin();
}
};
using PairIter = vector<pair<int, int>>::iterator;
what is using?
we need to write binary search, lower bound search
learn about binary search functions the natural one by god