leetcode62 Unique Paths

A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below).

The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked 'Finish' in the diagram below).

How many possible unique paths are there?

class Solution {
public:
int uniquePaths(int m, int n) {
/*      if(n==1)
return 1;
int ans=0;
vector<int> jlist(n-1,1);
for(int i=1;i<m;i++)
{
for(int j=0;j<n-1;j++)
{
if(j==0)
jlist[j]++;
else
jlist[j]+=jlist[j-1];
}
}
return jlist[n-2];*/
int ans=0;
vector<int> jlist(n,1);
for(int i=1;i<m;i++)
{
for(int j=1;j<n;j++)
jlist[j]+=jlist[j-1];
}
return jlist[n-1];
}
};

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