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#include<vector>
using namespace std;

int search(vector<int>& nums, int target) {
	int i = 0, j = nums.size()-1; //这里的类型别用auto, 否则后续
                                //mid - 1 可能溢出
    int mid;
	while (i <= j) {
		mid = (i + j ) / 2;
		if (nums[mid] == target) {
			return mid;
		}else if (nums[mid] > target)	j = mid-1; //注意此处 -1
		else i = mid+1; //以及此处 + 1
        //否则容易陷入死循环
	}
	return -1;
}