前缀和思维导图：

一维前缀和算法模版：

#include <iostream>

using namespace std;

const int N = 100010;

int n, m;
int s[N];

int main()
{
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i++)
    {
        int x;
        scanf("%d", &x);
        s[i] = s[i - 1] + x;  // 前缀和的初始化
    }

    while (m--)
    {
        int l, r;
        scanf("%d%d", &l, &r);
        printf("%d\n", s[r] - s[l - 1]);  // 区间和的计算
    }

    return 0;
}

二维前缀和算法模版：

#include <iostream>

using namespace std;

const int N = 1010;

int n, m, q, x;
int s[N][N];

int main()
{
    scanf("%d%d%d", &n, &m, &q);
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
        {
            scanf("%d", &x);
            s[i][j] = s[i - 1][j] + s[i][j - 1] - s[i - 1][j - 1] + x;
        }

    while (q--)
    {
        int x1, y1, x2, y2;
        scanf("%d%d%d%d", &x1, &y1, &x2, &y2);
        printf("%d\n", s[x2][y2] - s[x1 - 1][y2] - s[x2][y1 - 1] + s[x1 - 1][y1 - 1]);
    }

    return 0;
}