[LeetCode] Search for a Range

最新推荐文章于 2018-09-05 14:58:19 发布

原创最新推荐文章于 2018-09-05 14:58:19 发布 · 282 阅读

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本文介绍了一种高效搜索范围优化算法，通过改进二分查找过程，实现了目标值在数组中的精确定位，并扩展了搜索范围，提高了查找效率。

class Solution {
public:
    vector<int> searchRange(int A[], int n, int target) {
        vector<int> v;
        int equal,m,k;
        equal = index(A,n,target);
        if(equal == -1){
            v.push_back(-1);
            v.push_back(-1);
            return v;
        }else{
        m = k = equal;
        while(A[m - 1] == A[equal] && m > 0) m --;
        while(A[k + 1] == A[equal] && k < n - 1) k ++;
        v.push_back(m);
        v.push_back(k);
        return v;
        }
    }
    int index(int A[],int n,int num){
        int first = 0,end = n - 1,mid;
        int result = -1;
        while(first <= end){
            mid = (first + end)/2;
            if(A[mid] == num)
                return mid;
            else if(A[mid] > num)
                end = mid - 1;
            else
                first = mid + 1;
        }
        return result;
    }
};