[LeetCode] 64.最小路径和

   第一个：

class Solution {
    public int minPathSum(int[][] m) {
        if(m==null||m.length==0||m[0]==null||m[0].length==0){
            return 0;
        }

        int row=m.length;
        int col=m[0].length;
        int[][] dp=new int[row][col];
        dp[0][0] = m[0][0];
        for(int i=1;i<row;i++){
            dp[i][0]=dp[i-1][0]+m[i][0];
        }
        for(int i=1;i<col;i++){
            dp[0][i]=dp[0][i-1]+m[0][i];
        }
        for(int i=1;i<row;i++){
            for(int j=1;j<row;j++){
                dp[i][j] = Math.min(dp[i - 1][j], dp[i][j - 1]) + m[i][j];
            }
        }
        return dp[row - 1][col - 1];
    }
}

 第二种：把dp数组换成一维的

    public int minPathSum(int[][] grid) {
        if(grid == null || grid.length == 0) {
            return 0;
        }
        int m = grid.length, n = grid[0].length;
        int[] dp = new int[n];
        for(int i = 0; i < m; i++) {
            for(int j = 0; j < n; j++) {
                if(j == 0) {
                    dp[j] = dp[j] + grid[i][j];
                } else if (i == 0) {
                    dp[j] = dp[j - 1] + grid[i][j];
                } else {
                    dp[j] = Math.min(dp[j], dp[j - 1]) + grid[i][j];
                }
            }
        }
        return dp[n - 1];
    }