Given a boolean 2D matrix (0-based index), find whether there is path from (0,0) to (x,y) and if there is one path, print the minimum no of steps needed to reach it, else print -1 if the destination is not reachable. You may move in only four direction ie up, down, left and right. The path can only be created out of a cell if its value is 1.
Example:
Input:
2
3 4
1 0 0 0 1 1 0 1 0 1 1 1
2 3
3 4
1 1 1 1 0 0 0 1 0 0 0 1
0 3
Output:
5
3
Input: The first line of input contains an integer T denoting the no of test cases. Then T test cases follow. Each test case contains two lines . The first line of each test case contains two integers n and m denoting the size of the matrix. Then in the next line are n*m space separated values of the matrix. The following line after it contains two integers x and y denoting the index of the destination.
Output: For each test case print in a new line the min no of steps needed to reach the destination.
Code:
bool isSafe(int currRow,int currCol,int rows,int columns,vector<bool> visited[]) {
return currRow>=0 && currRow<rows && currCol>=0 && currCol<columns && !visited[currRow][currCol];
}
int minSteps(vector<int> matrix[],int n,int m,int x,int y) {
vector<bool> visited[n];
for(int i=0;i<n;i++){
vector<bool> tmp(m);
for(int j=0;j<m;j++){
if(matrix[i][j]==0){
tmp[j]=true;
} else {
tmp[j]=false;
}
}
visited[i]=tmp;
}
queue<pair<int,int>> q;
q.push(make_pair(0,0));
visited[0][0]=true;
int minDist[n][m];
for(int i=0;i<n;i++){
for(int j=0;j<m;j++){
minDist[i][j]=INT_MAX;
}
}
minDist[0][0]=0;
static int rows[]={0,1,0,-1};
static int columns[]={1,0,-1,0};
while(!q.empty()) {
pair<int,int> p=q.front();
q.pop();
for(int i=0;i<4;i++) {
if(isSafe(p.first+rows[i],p.second+columns[i],n,m,visited)) {
visited[p.first+rows[i]][p.second+columns[i]]=true;
q.push(make_pair(p.first+rows[i],p.second+columns[i]));
if(minDist[p.first+rows[i]][p.second+columns[i]]> minDist[p.first][p.second]+1) {
minDist[p.first+rows[i]][p.second+columns[i]] = minDist[p.first][p.second]+1;
}
}
}
}
if(minDist[x][y]!=INT_MAX) {
return minDist[x][y];
}
return -1;
}
Test Case Failing
Input:
20 13
0 1 1 1 1 0 0 0 1 1 1 1 0 0 0 0 0 1 1 1 0 1 0 1 1 0 0 1 0 1 0 1 0 1 0 1 1 0 0 0 1 1 0 1 1 0 1 1 1 0 1 1 0 1 0 1 1 0 0 1 1 0 0 0 0 0 1 1 1 1 0 0 1 0 0 0 0 1 0 1 0 1 0 0 0 0 1 1 0 1 0 1 0 1 1 0 1 1 1 0 0 1 1 1 1 1 0 1 0 0 0 0 1 0 0 1 0 1 0 0 1 0 0 1 1 1 1 1 0 0 1 1 0 0 0 1 1 0 1 0 0 1 0 1 0 1 0 0 0 0 1 1 1 1 0 0 0 1 1 1 0 1 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1 0 1 0 1 0 1 0 1 1 1 0 1 0 0 0 0 0 1 0 0 0 1 0 1 1 0 1 0 0 1 1 1 0 1 0 1 0 1 0 0 0 0 1 0 1 1 0 1 0 0 1 1 0 0 0 1 0 1 1 1 1 0 0 1 0 0 0 0 1 0 0 1 1 1 1 0 0 1 1 1 0 1
6 3
Its Correct output is:
-1
And Your Code's output is:
13
Algorithm:
1. Traverse the 2 d array from source using BFS.
2. Maintain 2 2d arrays visited and minDist.
3. Initialize values of visited as true whose value in array is 0 and rest as false; Initialize minDist to INT_MAX.
4. While traversing, validate if its a valid point using isSafen where it is checked if visited is false and point lies within 2d array size limits.
5. If point is safe, make visited for the point as true and push it in the queue.
6. Finlly check if mindist for the point is greater than its parent minDist + 1 ; Update accordingly.
But i am getting wrong answer; attached failing test case. Can someone explain where my algo is going wrong ?
