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目录
只出现一次的数字
cpp
class Solution {
public:
int singleNumber(vector<int>& nums) {
int res = 0;
for (auto e : nums) res ^= e;
return res;
}
};多数元素
常规哈希表。
cpp
class Solution {
public:
int majorityElement(vector<int>& nums) {
unordered_map<int, int> hashmap;
int n = nums.size() / 2;
int target = 0;
for (auto e : nums)
{
if (++hashmap[e] > n)
{
target = e;
break;
}
}
return target;
}
};投票法。
cpp
class Solution {
public:
int majorityElement(vector<int>& nums) {
int target = 0, cnt = 0;
for (auto e : nums)
{
if (e == target) cnt++;
else if (--cnt < 0)
{
target = e;
cnt = 1;
}
}
return target;
}
};颜色分类
cpp
class Solution {
public:
void sortColors(vector<int>& nums) {
int l = -1, r = nums.size(), i = 0;
while (i < r)
{
if (nums[i] == 0) swap(nums[++l], nums[i++]);
else if (nums[i] == 1) i++;
else swap(nums[--r], nums[i]);
}
}
};下一个排列
cpp
class Solution {
public:
void nextPermutation(vector<int>& nums) {
int i = nums.size() - 2;
while (i >= 0 && nums[i] >= nums[i + 1]) i--;
if (i >= 0)
{
int j = nums.size() - 1;
while (j >= 0 && nums[i] >= nums[j]) j--;
swap(nums[i], nums[j]);
}
reverse(nums.begin() + i + 1, nums.end());
}
};寻找重复数
cpp
class Solution {
public:
int findDuplicate(vector<int>& nums) {
int fast = 0, slow = 0;
do
{
slow = nums[slow];
fast = nums[nums[fast]];
} while (fast != slow);
slow = 0;
while (fast != slow)
{
slow = nums[slow];
fast = nums[fast];
}
return slow;
}
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