Merge Sorted Array
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 and n respectively.
解法一：从前往后，小的排最前。每次插入一个B，A需要整体后移。
class Solution { public: void merge(int A[], int m, int B[], int n) { int indA = 0; int indB = 0; int shift = 0; while(indA < m+shift && indB < n) { if(A[indA] <= B[indB]) indA++; else { for(int i = m-1+shift; i >= indA; i --) A[i+1] = A[i]; shift ++; A[indA++] = B[indB++]; } } if(indA >= m+shift) { while(indB < n) A[indA++] = B[indB++]; } } };
解法二：从后往前，大的排最后。不需要多余的移动。
class Solution { public: void merge(int A[], int m, int B[], int n) { int indA = m-1; int indB = n-1; for(int i = m+n-1; i >= 0; i --) { if(indA < 0) A[i] = B[indB--]; else if(indB < 0) return; else { if(A[indA] >= B[indB]) A[i] = A[indA--]; else A[i] = B[indB--]; } } } };
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原文：http://www.cnblogs.com/ganganloveu/p/3762953.html