宽度优先搜索，之前TLE是因为写成了深度优先搜索。
后来一次AC附上代码：

class Solution {
public:
    int rows;
    int cols;
    int minnow;
    int minPathSum(vector<vector<int> > &grid) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        rows = grid.size()-1;
        cols = grid[0].size()-1;</p>

<pre><code>    vector&amp;lt;vector&amp;lt;int&amp;gt;&amp;gt; copygrid(grid.size());
    int sum = 0;
    for(int i = 0;i &amp;lt; grid.size();i++)
    {
        for(int j = 0;j &amp;lt; grid[0].size();j++)
        {
            sum += grid[i][j];
        }
    }

    for(int i = 0;i &amp;lt; grid.size();i++)
    {
        vector&amp;lt;int&amp;gt; tmp(grid[0].size());
        for(int j = 0;j &amp;lt; grid[0].size();j++)
        {
            tmp[j] = sum;
        }
        copygrid[i] = tmp;
    }
    copygrid[0][0] = grid[0][0];

    int px[10000],py[10000];
    int cpx[20000],cpy[20000];
    int index = 0;
    px[index]   = 0;
    py[index++] = 0; 
    while(true)
    {
        int top = index;
        index = 0;
        for(int i = 0;i &amp;lt; top;i++)
        {
            int x = px[i];
            int y = py[i];
            if(x + 1 &amp;lt;= rows)
            {
                if(copygrid[x][y] + grid[x+1][y] &amp;lt; copygrid[x+1][y])
                {
                    copygrid[x+1][y] = copygrid[x][y] + grid[x+1][y];
                    cpx[index] = x+1;
                    cpy[index] = y;
                    index++;
                }
            }
            if(y + 1 &amp;lt;= cols)
            {
                if(copygrid[x][y] + grid[x][y+1] &amp;lt; copygrid[x][y+1])
                {
                    copygrid[x][y+1] = copygrid[x][y] + grid[x][y+1];
                    cpx[index] = x;
                    cpy[index] = y+1;
                    index++;
                }
            }
        }
        if(index == 0)
            break;
        for(int i = 0;i &amp;lt; index;i++)
        {
            px[i] = cpx[i];
            py[i] = cpy[i];
        }
    }
    return copygrid[rows][cols];
}
</code></pre>

<p>};