add new

Author: gitgou

addTwoNumbers.cpp

@@ -0,0 +1,49 @@
+struct ListNode {
+    int val;
+    ListNode *next;
+    ListNode() : val(0), next(nullptr) {}
+    ListNode(int x) : val(x), next(nullptr) {}
+    ListNode(int x, ListNode *next) : val(x), next(next) {}
+};
+
+class Solution {
+public:
+    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
+        ListNode * head = new ListNode();
+        ListNode * tmp = head;
+        int carry = 0;
+        while (l1 && l2)
+        {
+            tmp->next = new ListNode((l1->val + l2->val +carry) % 10);
+            carry = (l1->val + l2->val +carry) / 10;
+            tmp = tmp->next;
+            l1 = l1->next;
+            l2 = l2->next;
+        }
+
+        while (l1)
+        {
+            tmp->next = new ListNode((l1->val + carry) % 10);
+            carry = (l1->val + carry) / 10;
+            tmp = tmp->next;
+            l1 = l1->next;
+        }
+        
+        while (l2)
+        {
+            tmp->next = new ListNode((l2->val + carry) % 10);
+            carry = (l2->val + carry) / 10;
+            tmp = tmp->next;
+            l2 = l2->next;
+        }
+        
+        if(carry != 0){
+           tmp->next = new ListNode(carry); 
+        }
+
+        tmp = head;
+        head = head->next;
+        delete tmp;
+        return head;
+    }
+};

multiply_43.cpp

@@ -0,0 +1,32 @@
+#include<string>
+#include<iostream>
+#include<vector>
+using namespace std;
+class Solution {
+public:
+    string multiply(string num1, string num2) {
+        if(num1 == "0" || num2 == "0")
+            return "0";
+        string res;
+        int m = num1.size(), n = num2.size();
+        vector<int> arr(m + n); 
+        for(int index1 = m -1; index1 >= 0 ; --index1)
+        {
+            for(int index2 = n - 1; index2 >= 0; --index2){
+                int tmp1 = num1[index1] - '0', tmp2 = num2[index2] - '0';
+                arr[index1 + index2 + 1] += tmp1 * tmp2;
+            }
+        }
+
+        for(int i = m + n - 1; i > 0; --i){
+            int tmp = arr[i];
+            arr[i] = tmp % 10;
+            arr[i-1] = arr[i-1] + tmp / 10;
+        }
+        int start = arr[0] == 0 ? 1 : 0;
+        for(int i = start; i < m + n; ++i){
+            res.push_back(arr[i] + '0');
+        }
+        return res; 
+    }
+};