Steps: Add root to queue If left child not null, add it to queue If…
Category: Algorithms
std::map
Simple insert
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map<string, int> dataMap; // Two methods to insert // 1. Insert with pair dataMap.insert(pair<string, int>("TESTING", 1)); // 2. Insert with array dataMap["TESTING"] = 1; |
Access to second element using key (C++ 11)
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cout << dataMap.at("TESTING"); // Console output = 1 |
Iterate…
Unordered Map
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#include <unordered_map> using namespace std; unordered_map<int, int> map; map[2] = 4; // Map 4 to key value 2 auto p = map.find(3); //unordered_map<int, int>::const_iterator p = map.find(3); if (p != map.end()){ // Found } else{ // NOT Found } |
According to the documentation, the average searching complexity is O(1), by looking more into…
1. Two Sum
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class Solution { public: vector<int> twoSum(vector<int>& nums, int target) { vector<int> output; for (int i = 0; i < nums.size(); i++) for (int j = nums.size() - 1; j>i; j--) if (nums[i] + nums[j] == target) { output.push_back(i); output.push_back(j); return output; } } }; |
7. Reverse Integer
Reverse digits of an integer. Example1: x = 123, return 321 Example2: x = -123, return -321…
[ProjectEuler+] #8: Largest product in a series
Using string & substr instead of int for large result
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#include #include using namespace std; int main() { int T, N, K; string target; scanf("%d", &T); while (T--) { scanf("%d%d", &N, &K); cin >> target; string s = ""; int max = 0, temp = 1; for (int i = 0;i < (target.length() - K + 1);i++) // Loop until last k digits { temp = 1; s = target.substr(i, K); // Take k digits for (int j = 0;j < K;j++)// Split and multiply each digit temp *= atoi((s.substr(j, 1)).c_str()); // atoi for string to int if (temp > max) max = temp; } printf("%d\n", max); } return 0; } |
[ProjectEuler+] #6: Sum square difference
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#include #include using namespace std; int main() { long long T; scanf("%lld", &T); while (T--) { long long N, sum = 0; scanf("%lld", &N); N += 1; for (long long i = 1;i < N;i++) sum += pow(i, 2); N -= 1; printf("%lld\n", ((N*(1 + N) / 2)*(N*(1 + N) / 2) - sum)); } return 0; } |
[ProjectEuler+] #5: Smallest multiple
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#include #include #include using namespace std; int findPrime(int totalSize, vector &primeList) { int primeListSize = 1; bool isPrime; primeList[0] = 2; for (int i = 3;i <= totalSize;i += 2) // Skip even number, loop within "max" { isPrime = false; // reset to find prime for (int k = 0;k < primeListSize;k++) { if (i%primeList[k] == 0) // Not Prime { isPrime = false; break; } isPrime = true; // Survive the break = Prime } if (isPrime) { primeList[primeListSize] = i; // Store into array primeListSize++; } } return primeListSize; } int main() { int n, count = 0, max = 0; scanf("%d", &n); vector input(n); for (int i = 0;i < n;i++) { scanf("%d", &input[i]); if (input[i] > max) max = input[i]; } vector primeList(max); // Find only the MAX value prime array int primeListSize = findPrime(max, primeList); for (int i = 0;i < input.size();i++) { long long sum = 1; int j = 0, n = 1; while (true) { if (primeList[j] == 0) // Out of the primeList break; n = 1; while (pow(primeList[j], n) <= input[i]) n++; sum *= pow(primeList[j], n - 1); j++; } printf("%lld\n", sum); } return 0; } |
[Algorithms] Circular Array Rotation
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#include <iostream> #include <string> using namespace std; int main() { int n, k, q; scanf("%d%d%d", &n, &k, &q); while (k > n) // in case k exceeds n (cycle) { k %= n; } int* arr = new int[n]; int* num = new int[q]; int* head = new int[n - k]; int* tail = new int[k]; for (int i = 0;i < n;i++) { scanf("%d", &arr[i]); if (i < (n - k)) head[i] = arr[i]; // backup[] from 0 else if (i >= (n - k)) tail[i-(n-k)] = arr[i]; // tail[] from 0 } for (int i = 0;i < n;i++) { if (i < k) arr[i] = tail[i]; else arr[i] = head[i-k]; } for (int i = 0;i < q;i++) { scanf("%d", &num[i]); printf("%d\n", arr[num[i]]); } return 0; } |
[ProjectEuler+] #4: Largest palindrome product
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#include <iostream> using namespace std; int reverse(int oldNum){ int newNum = 0; while (oldNum > 0){ newNum = newNum * 10 + (oldNum % 10); oldNum = oldNum / 10; } return newNum; } int checkMultiple(int num){ for (int i = 100;i < 999;i++){ for (int j = 100;j < 999;j++) { if (i*j == num) return num; } } return -1; } int main() { int T; scanf("%d", &T); while (T--) { int N; // Since max value of int > 1,000,000 scanf("%d", &N); while (N--){ // Check if it's a palindrome number if (reverse(N) == N){ // Check if it's composed by product of two 3-digit number if (checkMultiple(N) != -1) { cout << N <<"\n"; break; } } } } return 0; } |