第一种方法
class Solution {
public:
int search(vector<int>& nums, int target) {
int sum = 0;
for(auto item : nums)
if(item == target)
sum++;
return sum;
}
};
第二种,二分搜索
class Solution {
public:
int search(vector<int>& nums, int target) {
int beg = findBeginPos(nums,target);
int end = findEndPos(nums,target);
if(beg == -1 && end == -1) return 0;
if(beg == -1 || end == -1) return 1;
return end - beg + 1;
}
int findEndPos(vector<int>nums,int target)
{
int left = 0;
int right = nums.size()-1;
while(left <= right) {
int mid;
mid = (right + left) / 2;
//如果中间值和目标值相等
if(nums[mid] == target) {
if(mid == nums.size() - 1|| nums[mid + 1] > target)
return mid;
left = mid + 1;
}else if(nums[mid] < target) {
left = mid + 1;
}else{
right = mid - 1;
}
}
return -1;
}
int findBeginPos(vector<int>nums,int target)
{
//左指针和右指针 指向两端
int left = 0; int right = nums.size() - 1;
while(left <= right) {
int mid;
mid = (right + left) / 2;
//如果中间值和目标值相等
if(nums[mid] == target) {
if(mid == 0 || nums[mid - 1] < target)
return mid;
right = mid -1;
}else if(nums[mid] > target) {
right = mid - 1;
}else{
left = mid + 1;
}
}
return -1;
}
};