HDUOJ 2086推导

已知A1=(A0+A2)/2 - C1, A2=(A1+A3)/2 - C2 , ...=>A1+A2 = (A0+A2+A1+A3)/2 - (C1+C2)=>A1+A2 = A0+A3 - 2(C1+C2) 类似的有：A1+A2 = A0+A3 - 2(C1+C2)A1+A3 = A0+A4 - 2(C1+C2+C3)A1+A4 = A0+A5 - 2(C1+C2+C3+C4)...A1+An = A0+An+1 - 2(C1+C2+...+Cn)A1+A1 = A0+A2 - 2(C1) (本来就是)----------------------------------------------------- 左右求和(n+1)A1+(A2+A3+...+An) = nA0 +(A2+A3+...+An) + An+1 - 2(nC1+(n-1)C2+...+2Cn-1+Cn)=> (n+1)A1=nA0 + An+1 - 2(nC1+(n-1)C2+...+2Cn-1+Cn)=> A1 = [nA0 + An+1 - 2(nC1+(n-1)C2+...+2Cn-1+Cn)]/(n+1)