第1周,(5-1)*2 = 8
第2周,(8-2)*2 = 12
第3周,(12-3)*2 = 18
……
这也能不会

#include <stdio.h> int main( void ) { for( unsigned i=1, n=5; n<=150; ++i ) { n = (n-i)*2; printf( "No.%u week, friends number = %u\n", i, n ); } return 0; }
#include <stdio.h> int main( void ) { for( unsigned i=1, n=5; n<=150; ++i ) { n = (n-i)*2; printf( "No.%u week, friends number = %u\n", i, n ); } return 0; }