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.
方法1:遇到这种题目无脑动态规划
class Solution {
public int minPathSum(int[][] grid) {
int m = grid.length, n = grid[0].length;
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (i == 0 && j == 0){
continue;
}
if (i == 0){
grid[0][j] += grid[0][j - 1];
}else if (j == 0){
grid[i][0] += grid[i - 1][0];
}else{
grid[i][j] += Math.min(grid[i - 1][j], grid[i][j - 1]);
}
}
}
return grid[m - 1][n - 1];
}
}
时间复杂度:O(m.n)
空间复杂度:O(1)