简单表示

集合S 去除一个元素{i} S/{i}……… S&(~1<< i)

特殊集合枚举

{0,1,2,3,…n−1} 所包含的特定大小为 k <script type="math/tex" id="MathJax-Element-81">k</script> 的子集

int comb = (1<<k)-1; while(comb < (1<<n)){ int x = comb & -comb,y = comb+x; comb = ((comb&~y) / x>>1 ) |y; }