private JumpItem MinimumNumberofJumpsDP(int[] input)
{
if (input.Length == 0 || input[0] == 0)
{
return(null);
}
int[] jumps = new int[input.Length];
int[] jumpvalues = new int[input.Length];
// Find the minimum number of jumps to reach arr[i] from 0 to i -1
// from arr[0], and assign this value to jumps[i]
jumps[0] = 0;
jumpvalues[0] = -1;
for (int i = 1; i < input.Length; i++)
{
jumps[i] = Int32.MaxValue; //Initialize with max and then we update with actual value
//Here we need to see whether we can reach i from 0 to i -1...
//Note i and j should not be equal because there is no reason to start and end at the same place. (No need to jump if the start and end are same)
for (int j = 0; j < i; j++)
{
//can we reach index i if we jump from j position
if (j + input[j] >= i && jumps[j] != Int32.MaxValue)
{
int steps = jumps[j] + 1;
if (steps < jumps[i])
{
//jumps[i] = min(jumps[i], jumps[j] + 1);
jumps[i] = steps;
jumpvalues[i] = j; //index where it came from
}
}
}
}
//Backtrack with jump values
StringBuilder sb = new StringBuilder();
int k = input.Length - 1;
sb.Insert(0, "," + input[k]);
while (k > 0)
{
int lastjumpfromIndex = jumpvalues[k];
sb.Insert(0, "," + input[lastjumpfromIndex]);
k = lastjumpfromIndex;
}
JumpItem result = new JumpItem();
result.MinimumJump = jumps[input.Length - 1]; //get the lasat item
result.Path = sb.ToString();
return(result);
}
private void button1_Click(object sender, EventArgs e)
{
//https://www.youtube.com/watch?v=cETfFsSTGJI
int[] input = AlgorithmHelper.ConvertCommaSeparetedStringToInt(this.textBox15.Text);
JumpItem result = MinimumNumberofJumpsDP(input);
this.textBox12.Text = result.MinimumJump.ToString();
this.textBox1.Text = result.Path;
}
