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Square Matrix Multiplication/main.cpp

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+#include <vector>
+#include <iostream>
+using std::size_t;
+
+std::vector<int> get_column(std::vector<std::vector<int>> input, int index){
+    std::vector<int> result;
+    for(int i = 0; i<input.size(); i++){
+        result.push_back(input[i][index]);
+    }
+    return result;
+}
+
+int multiply(std::vector<int> first, std::vector<int> second){
+    int result = 0;
+    for(int i = 0; i<first.size(); i++){
+        result += first[i] * second[i];
+    }
+    return result;
+}
+
+std::vector<std::vector<int>> matrix_multiplication(std::vector<std::vector<int>> &a, std::vector<std::vector<int>> &b, size_t n){
+    std::vector<std::vector<int>> result;
+    std::vector<int> row;
+    for(int i=0; i<n;i++){
+        for(int j=0; j<n; j++){
+            row.push_back(
+                multiply(a[i], get_column(b, j))
+            );
+        }
+        result.push_back(row);
+        row = {};
+    }
+    return result;
+}
+
+
+int main(){
+    std::vector<std::vector<int>> test1 = {{1,2},{3,4}};
+    std::vector<std::vector<int>> test2 = {{1,2},{3,4}};
+    std::vector<std::vector<int>> result = matrix_multiplication(test1, test2, 2);
+    std::cout << result[1][1];
+}
+

Sum Strings as Numbers/main.cpp

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+#include <string>
+#include <vector>
+#include <algorithm>
+#include <iostream>
+
+std::vector<std::string> sort_size(std::string &a, std::string &b){
+    if(a.size() <= b.size()){
+        return {a, b};
+    } else {
+        return {b, a};
+    }
+}
+
+void pad_zeros(std::string &input, int zeros_to_pad){
+    input.insert(0, zeros_to_pad, '0');
+}
+
+std::string sum_strings(std::string a, std::string b) {
+    a.erase(0, std::min(a.find_first_not_of('0'), a.size()-1));
+    b.erase(0, std::min(b.find_first_not_of('0'), b.size()-1));
+    auto shortest = sort_size(a, b);
+    int size_diff = abs(a.size() - b.size());
+
+    pad_zeros(shortest[0], size_diff);
+
+    int overflow = 0;
+    char insert;
+    std::string result;
+    for(int i=shortest[0].size()-1; i>=0; i--){
+        int val1 = shortest[1][i] - '0';
+        int val2 = shortest[0][i] - '0';
+        int temp = val1 + val2 + overflow;
+        if(temp>9){
+            overflow = temp / 10;
+            insert = std::to_string(temp)[1];
+        } else {
+            overflow = 0;
+            insert = std::to_string(temp)[0];
+        }
+        result.insert(0, 1, insert);
+    }
+
+    if(overflow > 0)
+        result.insert(0, std::to_string(overflow));
+
+    return result;
+}
+
+int main(){
+    std::string test1 = "99";
+    std::string test2 = "2";
+    std::cout << sum_strings(test1, test2);
+}