矩阵原地转置，空间复杂度为O(1)(暂时先保存下来)

#include<iostream>
using namespace std;

/* 后继 */
int getNext(int i, int m, int n)
{
return (i%n)*m + i/n;
}

/* 前驱 */
int getPre(int i, int m, int n)
{
return (i%m)*n + i/m;
}

/* 处理以下标i为起点的环 */
void movedata(int *mtx, int i, int m, int n)
{
int temp = mtx[i];  // 暂存
int cur = i;       // 当前下标
int pre = getPre(cur, m, n);
while(pre != i)
{
mtx[cur] = mtx[pre];
cur = pre;
pre = getPre(cur, m, n);
}
mtx[cur] = temp;
}

/* 转置，即循环处理所有环 */
void transpose(int *mtx, int m, int n)
{
for(int i=0; i<m*n; ++i)
{
int next = getNext(i, m, n);
while(next > i) // 若存在后继小于i说明重复
next = getNext(next, m, n);
if(next == i)   // 处理当前环
movedata(mtx, i, m, n);
}
}

/* 输出矩阵 */
void print(int *mtx, int m, int n)
{
for(int i=0; i<m*n; ++i)
{
if((i+1)%n == 0)
cout << mtx[i] << "\n";
else
cout << mtx[i] << " ";
}
}

/* 测试 */
int main()
{
int matrix[4*2] = {1,2,3,4,5,6,7,8};
cout << "Before matrix transposition:" << endl;
print(matrix, 4, 2);
transpose(matrix, 4, 2);
cout << "After matrix transposition:" << endl;
print(matrix, 2, 4);
return 0;
}