直接用一個carry記錄進位就可以

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1 //NEW 2 class Solution { 3 public ListNode addTwoNumbers(ListNode l1, ListNode l2) { 4 ListNode root = new ListNode(0); 5 return addTwoNumbers(l1, l2, root); 6 } 7 public ListNode addTwoNumbers(ListNode l1, ListNode l2, ListNode root){ 8 int carry = 0; 9 ListNode dummy = root; 10 while(l1 != null || l2!=null){ 11 int x = (l1 != null) ? l1.val : 0; 12 int y = (l2 != null) ? l2.val : 0; 13 dummy.next = new ListNode((carry + x + y)%10); 14 dummy = dummy.next; 15 carry = (carry + x + y)/10; 16 if(l1!=null) { 17 l1 = l1.next; 18 } 19 if(l2!=null) { 20 l2 = l2.next; 21 } 22 } 23 if (carry > 0) { 24 dummy.next = new ListNode(carry); 25 } 26 return root.next; 27 } 28 } 29 30 31 //Old 32 class Solution { 33 public ListNode addTwoNumbers(ListNode l1, ListNode l2) { 34 String str1 = "", str2 = ""; 35 while(l1 != null) { 36 str1 += Integer.toString(l1.val); 37 l1 = l1.next; 38 } 39 while(l2 != null) { 40 str2 += Integer.toString(l2.val); 41 l2 = l2.next; 42 } 43 char[] str11 = str1.toCharArray(); 44 char[] str21 = str2.toCharArray(); 45 char[] res = new char[Math.max(str11.length, str21.length) + 1]; 46 for(int i = 0; i < res.length; i++) { 47 res[i] = 'a'; 48 } 49 res[res.length - 1] = '0'; 50 int record = 0; 51 for(int i = 0; i < res.length; i++) { 52 if(i < str11.length && i < str21.length) { 53 if(str11[i]-'0' + str21[i]-'0' + record >= 10) { 54 res[i] = (char)('0'+ ((str11[i]-'0') + (str21[i]-'0') +record) % 10); 55 record = 1; 56 }else { 57 res[i] = (char)('0'+ (str11[i]-'0' + str21[i]-'0' +record)); 58 record = 0; 59 } 60 61 }else if(i < str21.length) { 62 if(str21[i]-'0' +record >= 10) { 63 res[i] = (char)('0'+ (str21[i]-'0' +record) % 10); 64 record = 1; 65 }else { 66 res[i] = (char)('0'+ (str21[i]-'0' +record)); 67 record = 0; 68 } 69 }else if(i < str11.length){ 70 if(str11[i]-'0' +record >= 10) { 71 res[i] = (char)('0'+ (str11[i]-'0' +record) % 10); 72 record = 1; 73 }else { 74 res[i] = (char)('0'+ (str11[i]-'0' +record)); 75 record = 0; 76 } 77 }else { 78 if(record == 1) { 79 res[i] = '1'; 80 } 81 } 82 } 83 ListNode node = new ListNode(res[0]-'0'); 84 ListNode head = node; 85 for(int i = 1; i < res.length; i++) { 86 if(i != res.length - 1 || res[i] == '1') { 87 node.next = new ListNode(res[i]-'0'); 88 node = node.next; 89 } 90 91 } 92 return head; 93 } 94 }

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轉載于:https://www.cnblogs.com/goPanama/p/9582440.html

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