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Good_Stones.cpp
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Good_Stones.cpp
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int goodStones(int n,vector<int> &arr){
vector<int> dp(n,0);
// 0 non visited element
// 1 bad stone
// 2 good stone
for(int i=0;i<n;i++){
if(dp[i] == 0){
int temp=i;
bool good = false;
while(dp[temp] != 1){
//0 or no movement case
if(arr[temp] == 0) break;
// mark visited
dp[temp] = 1;
// next index
temp += arr[temp];
//good stone or already a good stone
if(temp<0 || temp>=n || dp[temp] == 2){
good = true;
break;
}
}
//if good stone foound
// mark all index in the sequence as good elements
if(good){
temp = i;
while(temp>=0 && temp<n){
dp[temp] = 2;
temp += arr[temp];
}
}
}
}
int ans=0;
for(int i=0;i<n;i++){
if(dp[i] == 2){
ans++;
}
}
return ans;
}