题解 | 二分查找-I

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) {
        // write code here
        // special case
        switch (nums.size()) {
            case 0: return -1;
            case 1: if(target==nums[0]) return 0;
            case 2: if(target==nums[0]) return 0; else if(target==nums[1]) return 1; else return -1;
            default: ;
        }
        // board case
        if(target<nums[0]) return -1;
        else if(target>nums[nums.size()-1]) return -1;
        // search
        int left = 0, right = nums.size() - 1, middle = nums.size() / 2;

        while (left < right) {
            if(left == right -1){
                if(target==nums[left]) return left;
                else if (target==nums[right]) return right;
                else return -1;
            }else{
                if(target==nums[middle]){
                    return middle;
                }else if(target>nums[middle]){
                    left = middle;
                }else{
                    right = middle;
                }
                middle = (left + right) / 2;
            }
        }
        return -1;
    }
};