Medium
Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.
Note: You can only move either down or right at any point in time.
简单题，但不会用二位滚动数组
class Solution {
public int minPathSum(int[][] grid) {
if (grid == null || grid.length == 0 || grid[0].length == 0){
return 0;
}
int n = grid.length;
int m = grid[0].length;
int[][] f = new int[n][m];
f[0][0] = grid[0][0];
for (int i = 1; i < m; i++){
f[0][i] = f[0][i - 1] + grid[0][i];
}
for (int i = 1; i < n; i++){
f[i][0] = f[i - 1][0] + grid[i][0];
}
//function
for (int i = 1; i < n; i++){
for (int j = 1; j < m; j++){
f[i][j] = Math.min(f[i][j - 1], f[i - 1][j]) + grid[i][j];
}
}
//answer
return f[n - 1][m - 1];
}
}
