PAT A1104

如果采用单纯的暴力枚举，会出现超时问题，可以跟绝递推来找出来规律；代码如下：#include<iostream>#include<stdlib.h>#include<stdio.h>#include<cstring>#include<math.h>using namespace std;const int maxn=100100;double data[maxn];int mem[maxn];int main(){ int n; double sum=0.0; scanf("%d",&n); for(int i=0;i<n;i++){ scanf("%lf",&data[i]); sum+=data[i](n-i)(i+1); } printf("%.2lf",sum); system(“pause”); return 0;}