View Compilation Error

0_0_18148121_16228.cpp: In function 'int gaosi(int, int)':
0_0_18148121_16228.cpp:57:41: error: 'swap' was not declared in this scope
                 swap(A[k][i],A[max_r][i]);
                                         ^
0_0_18148121_16228.cpp: In function 'int gauss(int, int)':
0_0_18148121_16228.cpp:91:41: error: 'swap' was not declared in this scope
                     swap(A[r][k],A[i][k]);
                                         ^
0_0_18148121_16228.cpp: In function 'int main()':
0_0_18148121_16228.cpp:123:5: error: 'cin' was not declared in this scope
     cin>>T;
     ^