什么是前缀和

前缀和的逆

它是前缀和的转变 a[i] = pre[i] - pre[i - 1]

Code:

#include <bits/stdc++.h>
    
using namespace std; 
const int N = 105;

int pre[N];

int main() { 
    int N; cin >> N;
    for (int i = 1; i <= N; i++) {
        cin >> pre[i];
    }
    for (int i = 1; i <= N; i++) {
        cout << pre[i] - pre[i - 1] << " \n"[i == N];
    }
    return 0;
}

Index * A

求出连续长度为M的子数组B的 i * Bi + M * Bm的最大值

Code: