Silver Following Directions

Debugging Help
#1

What is the difference between these two solutions for Silver Following Directions?
The first solution is my code after reading the analysis.
The second solution is Danny Mittal’s code translated into C++.
I understand the problem conceptually, I just can’t find the bug in solution 1.

Solution 1:

#include<bits/stdc++.h>
using namespace std;

// grid of signposts, 'R'=1, 'D'=0;
bool grid[1502][1502];
// how many cows pass through i,j
int A[1502][1502];
// cost of vats
int cost[1502][1502];

int main(){
    int n; cin>>n;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            char c; cin>>c;
            grid[i][j]=(c=='R');
        }
        cin>>cost[i][n+1];
    }
    for(int i=1;i<=n;i++) cin>>cost[n+1][i];

    // calculate starting values of A and answer
    int ans=0;
    for(int i=1;i<=n+1;i++){
        for(int j=1;j<=n+1;j++){
            if(i==n+1||j==n+1) ans+=A[i][j]*cost[i][j];
            else {
                A[i][j]++;
                if(grid[i][j]) A[i][j+1]+=A[i][j];
                else A[i+1][j]+=A[i][j];
            }
        }
    }

    // print original value of answer
    cout<<ans<<"\n";

    int q; cin>>q;
    for(int k=0;k<q;k++){
        ans=0;
        int i,j;
        cin>>i>>j;

        // recalculate old path
        int r=i,c=j;
        while(r!=n+1&&c!=n+1){
            r+=!grid[r][c];
            c+=grid[r][c];
            A[r][c]-=A[i][j];
        }

        // flip the sign
        grid[i][j]=!grid[i][j];

        // calculate new path
        r=i,c=j;
        while(r!=n+1&&c!=n+1){
            r+=!grid[r][c];
            c+=grid[r][c];
            A[r][c]+=A[i][j];
        }

        // calculate new answer
        for(int l=1;l<=n;l++){
            ans+=A[n+1][l]*cost[n+1][l];
            ans+=A[l][n+1]*cost[l][n+1];
        }
        cout<<ans<<"\n";
    }
}

Solution 2:

#include<bits/stdc++.h>
using namespace std;

string dirs[1502];
int weights[1502][1502];

int main(){
    int n; cin>>n;
    for(int y=0;y<n;y++){
        string c; cin>>c;
        dirs[y]=c;
        cin>>weights[y][n];
    }
    for(int x=0;x<n;x++){
        cin>>weights[n][x];
    }

    int amtReach[n+1][n+1];
    for(int i=0;i<=n;i++){
        for(int j=0;j<=n;j++){
            amtReach[i][j]=0;
        }
    }
    int answer=0;
    for (int y = 0; y <= n; y++) {
        for (int x = 0; x <= n; x++) {
            if (y == n || x == n) {
                answer += amtReach[y][x] * weights[y][x];
            } else {
                amtReach[y][x]++;
                if (dirs[y][x] == 'R') {
                    amtReach[y][x + 1] += amtReach[y][x];
                } else {
                    amtReach[y + 1][x] += amtReach[y][x];
                }
            }
        }
    }

    cout<<answer<<"\n";
    int k; cin>>k;
    for (int q = k; q > 0; q--) {
        int y,x;
        cin>>y>>x;
        y--,x--;

        int v = y;
        int u = x;
        while (v != n && u != n) {
            if (dirs[v][u] == 'R') {
                u++;
            } else {
                v++;
            }
            amtReach[v][u] -= amtReach[y][x];
        }
        answer -= amtReach[y][x] * weights[v][u];

        if (dirs[y][x] == 'R') {
            dirs[y][x] = 'D';
        } else {
            dirs[y][x] = 'R';
        }

        v = y;
        u = x;
        while (v != n && u != n) {
            if (dirs[v][u] == 'R') {
                u++;
            } else {
                v++;
            }
            amtReach[v][u] += amtReach[y][x];
        }
        answer += amtReach[y][x] * weights[v][u];

        cout<<answer<<"\n";
    }
}
#2

\quad