Search for a Range - Leetcode

本博客介绍了一个在有序数组中查找指定目标值起始和结束位置的算法,利用二分查找优化效率至O(log n)。通过示例说明了如何实现并应用这一方法。

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public class Solution {
    public int[] searchRange(int[] A, int target) {
        int start=0, end=A.length-1, mid, pivot=0;
        while(start<=end){
            mid = (start+end)/2;
            if(A[mid] == target){
                pivot = mid;
                break;
            }else if(target > A[mid])
                start=mid+1;
            else
                end=mid-1;
        }
       <span style="background-color: rgb(255, 204, 204);"> if(A[pivot]!=target)
        return new int[]{-1,-1};</span>
        
        int start1=0, end1=pivot, mid1;
        while(start1 <= end1){
            mid1 = (start1+end1)/2;
            if(A[mid1] == target)
                end1=mid1-1;
            else
                start1=mid1+1;
        }
        int new_low = <span style="background-color: rgb(255, 255, 51);">start1</span>;
        
        int start2=pivot+1, end2 = A.length-1, mid2;
        while(start2 <= end2){
            mid2 = (start2+end2)/2;
            if(A[mid2] == target)
                start2=mid2+1;
            else
                end2=mid2-1;
        }
        int new_high = <span style="background-color: rgb(255, 255, 51);">end2</span>;
        
        return new int[]{new_low,new_high};
    }
}



分析:数组是有序的,找到一个值两边的index。O(log n) 暗示二叉搜索,这里考点就是如何设置Middle

Given a sorted array of integers, find the starting and ending position of a given target value.

Your algorithm's runtime complexity must be in the order of O(log n).

If the target is not found in the array, return [-1, -1].

For example,
Given [5, 7, 7, 8, 8, 10] and target value 8,
return [3, 4].


资源下载链接为: https://pan.quark.cn/s/d9ef5828b597 在本文中,我们将探讨如何通过 Vue.js 实现一个带有动画效果的“回到顶部”功能。Vue.js 是一款用于构建用户界面的流行 JavaScript 框架,其组件化和响应式设计让实现这种交互功能变得十分便捷。 首先,我们来分析 HTML 代码。在这个示例中,存在一个 ID 为 back-to-top 的 div 元素,其中包含两个 span 标签,分别显示“回到”和“顶部”文字。该 div 元素绑定了 Vue.js 的 @click 事件处理器 backToTop,用于处理点击事件,同时还绑定了 v-show 指令来控制按钮的显示与隐藏。v-cloak 指令的作用是在 Vue 实例渲染完成之前隐藏该元素,避免出现闪烁现象。 CSS 部分(backTop.css)主要负责样式设计。它首先清除了一些默认的边距和填充,对 html 和 body 进行了全屏布局,并设置了相对定位。.back-to-top 类则定义了“回到顶部”按钮的样式,包括其位置、圆角、阴影、填充以及悬停时背景颜色的变化。此外,与 v-cloak 相关的 CSS 确保在 Vue 实例加载过程中隐藏该元素。每个 .page 类代表一个页面,每个页面的高度设置为 400px,用于模拟多页面的滚动效果。 接下来是 JavaScript 部分(backTop.js)。在这里,我们创建了一个 Vue 实例。实例的 el 属性指定 Vue 将挂载到的 DOM 元素(#back-to-top)。data 对象中包含三个属性:backTopShow 用于控制按钮的显示状态;backTopAllow 用于防止用户快速连续点击;backSeconds 定义了回到顶部所需的时间;showPx 则规定了滚动多少像素后显示“回到顶部”按钮。 在 V
### LeetCode 475 Heaters Problem Solution and Explanation In this problem, one needs to find the minimum radius of heaters so that all houses can be warmed. Given positions of `houses` and `heaters`, both represented as integer arrays, the task is to determine the smallest maximum distance from any house to its nearest heater[^1]. To solve this issue efficiently: #### Binary Search Approach A binary search on answer approach works well here because increasing the radius monotonically increases the number of covered houses. Start by sorting the list of heaters' locations which allows using binary search for finding closest heater distances quickly. ```python def findRadius(houses, heaters): import bisect houses.sort() heaters.sort() max_distance = 0 for house in houses: pos = bisect.bisect_left(heaters, house) dist_to_right_heater = abs(heaters[pos] - house) if pos < len(heaters) else float('inf') dist_to_left_heater = abs(heaters[pos-1] - house) if pos > 0 else float('inf') min_dist_for_house = min(dist_to_right_heater, dist_to_left_heater) max_distance = max(max_distance, min_dist_for_house) return max_distance ``` This code snippet sorts the lists of houses and heaters first. For each house, it finds the nearest heater either directly or indirectly (to the left side). It calculates the minimal distance between these two options and updates the global maximal value accordingly[^3]. The constraints specify that numbers of houses and heaters do not exceed 25000 while their positions range up to \(10^9\)[^2], making efficient algorithms like binary search necessary due to large input sizes involved.
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