试题:
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.
Example:
Input:
[
[1,3,1],
[1,5,1],
[4,2,1]
]
Output: 7
Explanation: Because the path 1→3→1→1→1 minimizes the sum.
代码:
class Solution {
public int minPathSum(int[][] grid) {
if (grid==null || grid.length == 0 || grid[0].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 (i==0 && j==0) {
dp[j] = grid[i][j];
} else if (i == 0) {
dp[j] = dp[j - 1] + grid[i][j];
} else if(j==0){
dp[j] = dp[j] + grid[i][j];
}else{
dp[j] = Math.min(dp[j-1] + grid[i][j], dp[j] + grid[i][j]);
}
}
}
return dp[n - 1];
}
}