题解 | #最小面积子矩阵#前缀和模板题，记住就行。

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        int k = sc.nextInt();
        int[][] matrix = new int[n][m];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                matrix[i][j] = sc.nextInt();
            }
        }
        int[][] prefixSum = new int[n + 1][m + 1];
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m; j++) {
                prefixSum[i][j] = matrix[i - 1][j - 1] + prefixSum[i - 1][j] + prefixSum[i][j - 1] - prefixSum[i - 1][j - 1];
            }
        }
        int ans = Integer.MAX_VALUE;
        for (int x1 = 1; x1 <= n; x1++) {
            for (int y1 = 1; y1 <= m; y1++) {
                for (int x2 = x1; x2 <= n; x2++) {
                    for (int y2 = y1; y2 <= m; y2++) {
                        int sum = prefixSum[x2][y2] - prefixSum[x1 - 1][y2] - prefixSum[x2][y1 - 1] + prefixSum[x1 - 1][y1 - 1];
                        if (sum >= k) {
                            int area = (x2 - x1 + 1) * (y2 - y1 + 1);
                            if (area < ans) ans = area;
                        }
                    }
                }
            }
        }
        System.out.println(ans == Integer.MAX_VALUE ? -1 : ans);
    }
}