二分查找

class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param nums int整型vector
     * @param target int整型
     * @return int整型
     */
    int search(vector<int>& nums, int target) {
        int index = -1, left = 0, right = nums.size() - 1;
        while (left <= right) {
            int mid = left + right >> 1;
            int val = nums[mid];
            if (target == val) {
                index = mid;
                break;
            }
            if (target < val) {
                right = mid - 1;
            } else {
                left = mid + 1;
            }
        }
        return index;
    }
};