Merge Sorted Array

最新推荐文章于 2024-01-18 17:58:46 发布

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最新推荐文章于 2024-01-18 17:58:46 发布

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分类专栏： leetcode

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本文介绍了一种将两个已排序的整数数组A和B合并为一个排序数组的方法。提供了两种实现方式，一种是从数组头部开始合并，另一种是从尾部开始合并以减少元素移动，提高效率。

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Given two sorted integer arrays A and B, merge B into A as one sorted array.

Note:
You may assume that A has enough space (size that is greater or equal to m + n) to hold additional elements from B. The number of elements initialized in A and B are m andn respectively.

方法一：从前往后
public class Solution {   //runtime = 247ms
    public void merge(int A[], int m, int B[], int n) {
    	int i = 0;
        if (m == 0){
        	for (i = 0; i < n; i ++){
        		A[i] = B[i];
        	}
        }
        int j = 0;
        int l;
        int h;
        while (i < m && j < n){
        	if (A[i] > B[j]){
        		l = i;
        		h = m;
        		while (l < h){
            		A[h] = A[h - 1];
            		h --;
            	}
            	A[i] = B[j];
        		System.out.print(A[i] + ",");
               	i ++;
               	j ++;
               	m ++;
               	}
        	else {
        		i++;
        		}
        	System.out.print(A[i] + ",");
        	}
        while (j < n){   //当A遍历结束而B还没遍历完时，直接将B中剩下的元素赋值给A
        	A[m] = B[j];
        	j ++;
        	m ++;
        }
        for (i = 0; i < m; i ++){
        	System.out.print(A[i] + ",");
        }
    }
}

方法二：从后往前，省去移动的时间
public class Solution {   //runtime = 212ms
	 public void merge(int A[], int m, int B[], int n) {
		 int k = m + n - 1;
		 int i = m - 1;
		 int j = n - 1;
		 while (j >= 0){
			 if (i >= 0 && (A[i] > B[j])){
				 A[k --] = A[i --];
			 }
			 else {
				 A[k --] = B[j --];
			 }
		 }
		 for (i = 0; i < m + n; i ++){
	        	System.out.print(A[i] + ",");
	        }
	 }
}