Leet Code ques Unique Paths

#1

Question is same but we are getting the wrong answer there

#2

int uniquePaths(int m, int n) {
long long int ans;
vector<vector> v(m+1,vector(n+1,1));
//at each cell we can come from left or top
for(int i=1;i<=m;i++)
{
for(int j=1;j<=n;j++)
{
v[i][j] = v[i-1][j]+v[i][j-1];
}
}
return v[m-1][n-1];

}
#3

Please save your code on the online IDE and share it with me here.

#4

I have corrected your code. You started calculating from the (m,n) and calculated the paths till 0,0,
so technically you calculated the result for m+1 rows and n+1 columns whereas we needed to solve it for m rows and n columns. In order to resolve this. You can either
start from m-1 row and n-1 column and calculate till (0,0)
Or
start from m row and n column and calculate till (1,1)
I have corrected your code and here’s the accepted solution
class Solution {
public int uniquePaths(int m, int n) {

    int[][] strg = new int[m+2][n+2];
	
	for(int row=m;row>=0;row--) {
		
		for(int col=n;col>=0;col--) {
			if(row==m && col ==n) {
				strg[m][n] = 1;
			}else {
				strg[row][col] = strg[row][col+1] + strg[row+1][col];
			}
		}
	}

// correction here: should start calculating from 1,1 and not 0,0
return strg[1][1];
}
}

#5

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