数字三角形

递归

int solve(int i,int j)
{
    return a[i][j]+(i==n?0:max(solve(i+1,j),slove(i+1,j+1)));
}

1. 时间效率低
2. 重复计算
   pass

递推

int i,j;
for (j=1;j<=n;j++)
    d[n][j]=a[n][j];
for (i=n-1;i>=1;i--)
    for (j=1;j<=i;j++)
        d[i][j]=a[i][j]+max(d[i+1][j],d[i+1][j+1]);

记忆化搜索

int solve(int i,int j)
{
    if (d[i][j]>=0)
        return d[i][j];
    return d[i][j]=a[i][j]+(i==n?0:max(solve(i+1,j),slove(i+1,j+1)));
}