64. Minimum Path Sum - cocoder39/coco39_LC GitHub Wiki

class Solution:
    def minPathSum(self, grid: List[List[int]]) -> int:
        m, n = len(grid), len(grid[0])
        
        dp = [[0] * n for i in range(m)]
        
        dp[0][0] = grid[0][0]
        for i in range(1, n):
            dp[0][i] = dp[0][i-1] + grid[0][i]
        for i in range(1, m):
            dp[i][0] = dp[i-1][0] + grid[i][0]
        
        for i in range(1, m):
            for j in range(1, n):
                dp[i][j] = grid[i][j] + min(dp[i-1][j], dp[i][j-1])
        
        return dp[m-1][n-1]

int minPathSum(vector<vector<int>>& grid) {
        int m = grid.size();
        if (m == 0) {
            return 0;
        }
        int n = grid[0].size();
        
        vector<vector<int>> dp(2, vector<int>(n));
        dp[0][0] = grid[0][0];
        for (int i = 1; i < n; i++) {
            dp[0][i] = grid[0][i] + dp[0][i - 1];
        }
        
        int pre = 0, cur = 1;
        for (int i = 1; i < m; i++) {
            dp[cur][0] = grid[i][0] + dp[pre][0];
            for (int j = 1; j < n; j++) {
                dp[cur][j] = grid[i][j] + min(dp[pre][j], dp[cur][j - 1]);
            }
            swap(pre, cur);
        }
        return dp[pre][n - 1];
    }