差分数组

对于一个数组D,要求其前i项和,$ SUM = \sum\limits_{i=1}^{n} {D_i}$ 令$f[i] = D[i] - D[i-1]      i \in [2, n]$, 当i=1时$f[1] = D[1] - 0 = D[1]$ 简单性质: D[i]的值是f[i]的前缀和,即$D[i] =  \sum\limits_{j=1}^{i} {f_i}$ 计算D[i]的前缀和, $ SUM = \sum\limits_{i=1}^{n} {D_i} = \s...