35 Search Insertion position

最新推荐文章于 2025-01-13 15:16:10 发布

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最新推荐文章于 2025-01-13 15:16:10 发布

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原文链接：http://www.cnblogs.com/77rousongpai/p/4521443.html

本文详细解析了使用二分查找算法解决搜索插入位置问题的方法，包括找到大于等于目标值的第一个位置和小于等于目标值的最后一个位置。通过比较不同实现方式的效率与优缺点，为读者提供了一种高效且简洁的解决方案。

public class Solution {
    public int searchInsert(int[] nums, int target) {
        if(nums == null || nums.length == 0) {
            return 0;
        }
        int res = 0;
        for (int i = 0; i < nums.length; i++) {
            if (nums[i] == target) {
                return i;
            } 
            if (nums[i] < target) {
                continue;
            }
            if (nums[i] > target) {
                res = i;
                return res;
            }
        }
        res = nums.length;
        return res;
    }
}

以上是自己写的

参考九章答案：用二分

find the first position >= target

public class Solution {
    public int searchInsert(int[] nums, int target) {
        int start = 0;
        int end = nums.length -1;
        
        while (start + 1 < end) {
            int mid = start + (end - start)/2;
            if (nums[mid] == target) {
                return mid;
            } else if (nums[mid] < target) {
                start = mid;
            } else {
                end = mid;
            }
        }
        
        if (nums[start] >= target) {
            return start;
        } else if (nums[end] >= target) {
            return end;
        } else {
            return end+1;
        }
    }
}

find the last position <= target

public class Solution {
    public int searchInsert(int[] A, int target) {
        int start = 0;
        int end = A.length - 1;
        int mid;
        
        if (target < A[0]) {
            return 0;
        }
        // find the last number less than target
        while (start + 1 < end) {
            mid = start + (end - start) / 2;
            if (A[mid] == target) {
                return mid;
            } else if (A[mid] < target) {
                start = mid;
            } else {
                end = mid;
            }
        }
        
        if (A[end] == target) {
            return end;
        }
        if (A[end] < target) {
            return end + 1;
        }
        if (A[start] == target) {
            return start;
        }
        return start + 1;
    }
}