class Solution {
public int[] twoSum(int[] nums, int target) {
Map<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
int complement = target - nums[i];
if (map.containsKey(complement)) {
return new int[] { map.get(complement), i };
}
map.put(nums[i], i);
}
throw new IllegalArgumentException("No two sum solution");
}
}
2. 添加兩數(shù) (Add Two Numbers)
解題思路
使用鏈表表示兩個數(shù)，從最低位開始逐位相加，注意處理進位。
實現(xiàn)代碼
class Solution {
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode dummyHead = new ListNode(0);
ListNode p = l1, q = l2, current = dummyHead;
int carry = 0;
while (p != null || q != null) {
int x = (p != null) ? p.val : 0;
int y = (q != null) ? q.val : 0;
int sum = carry + x + y;
carry = sum / 10;
current.next = new ListNode(sum % 10);
current = current.next;
if (p != null) p = p.next;
if (q != null) q = q.next;
}
if (carry > 0) {
current.next = new ListNode(carry);
}
return dummyHead.next;
}
}
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