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Remove_Linked_List_Elements.cpp
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Remove_Linked_List_Elements.cpp
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//////////////////////////////////////////////////////
// Project: MyLeetCode
//
// Author: YanShicong
// Date: 2016/08/10
//////////////////////////////////////////////////////
/*--------------------------------------------------------------------------------------------------------------
* Remove all elements from a linked list of integers that have value val.
*
* Example
* Given: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6
* Return: 1 --> 2 --> 3 --> 4 --> 5
//--------------------------------------------------------------------------------------------------------------*/
#include "../include/include.h"
// 时间复杂度O(n),空间复杂度O(1)
// 一遍遍历,两个指针prev和node,遇到同值就删除。
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* removeElements(ListNode* head, int val) {
if (!head) return head;
ListNode dummy(-1);
dummy.next = head;
ListNode *node(head), *prev(&dummy);
while(node)
{
if (node->val == val)
{
prev->next = node->next;
node = node->next;
}else
{
prev = node;
node = node->next;
}
}
return dummy.next;
}
};
//--------------------------------------------------------------------------------------------------------------
TEST_CASE("Remove_Linked_List_Elements", "[Linked Lists]"){
Solution s;
SECTION("Empty Input"){
REQUIRE(s.removeElements(NULL, 1) == NULL);
}
SECTION("Normal Input"){
ListNode a1(1),a2(1);
a1.next = &a2;
REQUIRE(s.removeElements(&a1, 1) == NULL);
ListNode b1(1),b2(2),b3(2),b4(3);
b1.next = &b2;
b2.next = &b3;
b3.next = &b4;
int r[2] = {1,3};
REQUIRE(get_nodes_val(s.removeElements(&b1, 2)) == vector<int>(r,r+2));
}
}