二分查找不用说，主要是这里注意如何找到数组中等于target的最左边和最右边的索引位置
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class Solution {
public:
vector<int> searchRange(vector<int>& nums, int target) {
vector<int> res = {-1, -1};
int rightIndex = findRightIndex(nums, target);
if (rightIndex < 0 || nums[rightIndex] != target) return res;
int leftIndex = findLeftIndex(nums, target);
res[0] = leftIndex;
res[1] = rightIndex;
return res;
}
int findLeftIndex(vector<int>& nums, int target) {
int lo = 0, hi = nums.size() - 1;
while (lo <= hi) {
int mid = lo + (hi - lo) / 2;
if (nums[mid] < target) lo = mid + 1;
else hi = mid - 1;
}
return lo;
}
int findRightIndex(vector<int>& nums, int target) {
int lo = 0, hi = nums.size() - 1;
while (lo <= hi) {
int mid = lo + (hi - lo) / 2;
if (nums[mid] > target) hi = mid - 1;
else lo = mid + 1;
}
return hi;
}
};
