题解 | #矩阵的最小路径和#

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int n = in.nextInt();
            int m = in.nextInt();
            int[][] matrix = new int[n][m];
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < m; j++) {
                    matrix[i][j] = in.nextInt();
                }
            }
            System.out.println(minPathSum(matrix));
        }
    }
    
    public static int minPathSum(int[][] matrix) {
        if (matrix == null || matrix.length < 1 || matrix[0] == null || matrix[0].length < 1) {
            return 0;
        }
        int n = matrix.length;
        int m = matrix[0].length;
        int[][] dp = new int[n][m];
        // dp[0][j]
        dp[0][0] = matrix[0][0];
        for (int j = 1; j < m; j++) {
            dp[0][j] = dp[0][j - 1] + matrix[0][j];
        }
        // dp[i][0]
        for (int i = 1; i < n; i++) {
            dp[i][0] = dp[i - 1][0] + matrix[i][0];
        }
        for (int i = 1; i < n; i++) {
            for (int j = 1; j < m; j++) {
                dp[i][j] = Math.min(dp[i - 1][j] + matrix[i][j], dp[i][j - 1] + matrix[i][j]);
            }
        }
        return dp[n - 1][m - 1];
    }
    
}