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i'm trying to solve a dp problem involves bitmasks and when i see others code, all of them have the these lines
for(mask = 0; mask < (1 << k); mask++){
..
for(submask = (mask - 1) & mask; submask > 0; submask = (submask - 1) & mask){
..
}
what these lines means ?
It iterates all over subsets consist of only bit 1 of mask.
For example if mask = 6 (110 in binary representation), then it iterates over 6 (110), 4(100), 2(010).
Edit: Sorry, I thought it was submask = mask. Because it initialize submask = (mask-1) & mask so it will iterates over 4 and 2 only.
First loop iterate masks in range 0 to 2^k — 1. Second loop iterate all submasks of current mask. This code works on O(3^k). Read this.