Bubble Cup 12 - Finals [Online Mirror, unrated, Div. 1] E. Product Tuples
题意略,题解生成函数练习题,1+(q-ai)x卷积即可,线段树优化(类似分治思想)//#pragmaGCCoptimize(2)//#pragmaGCCoptimize(3)//#pragmaGCCoptimize(4)//#pragmaGCCoptimize("unroll-loops")//#pragmacomment(linker,"/stack:200000000")//#pragmaGC