Create 2751. Robot Collisions (#528)

Author: Chayandas07

2751. Robot Collisions

@@ -0,0 +1,64 @@
+class Solution {
+public:
+void segmentUpdate(int l,int le,int re,vector<pair<int,int>>&h){
+    int i=le,j=le+1;
+    while(i>=l&&j<=re){
+        if(h[i].second==0){i--;continue;}
+        if(h[j].second==0){j++;continue;}
+        if(h[i].second > h[j].second){
+            h[i].second--;h[j++].second=0;
+        }else if(h[i].second < h[j].second){
+            h[j].second--;h[i--].second=0;
+        }else{
+            h[i].second=0;i--;
+            h[j].second=0;j++;
+        }
+    }
+}
+void update(vector<pair<int,int>>&h,vector<pair<int,char>>&d){
+    int i=0;
+    while(i<d.size()){
+        int le=i-1,re;
+        while(le+1<d.size()&&(h[le+1].second==0||d[le+1].second=='R'))le++;
+        re=le;
+        while(re+1<d.size()&&(h[re+1].second==0||d[re+1].second=='L'))re++;
+        if(le==i-1){i=re+1;continue;}
+        if(re==le)break;
+        segmentUpdate(i,le,re,h);
+        i=re+1;
+    }
+}
+
+bool collision(vector<pair<int,int>>&h,vector<pair<int,char>>&d){
+    int right=d.size(),left=-1;
+    for(int i=0;i<d.size();i++){
+        if(h[i].second){
+            if(d[i].second=='L')left=i;
+            else if(right==d.size())right=i;
+        }
+    }
+    return right<left;
+}
+    vector<int> survivedRobotsHealths(vector<int>& po, vector<int>& he, string di) {
+        vector<pair<int,int>>h;
+        vector<pair<int,char>>d;
+        for(int i=0;i<po.size();i++){
+            h.push_back({po[i],he[i]});
+            d.push_back({po[i],di[i]});
+        }
+        sort(h.begin(),h.end());
+        sort(d.begin(),d.end());
+        
+        while(collision(h,d))update(h,d);
+
+        vector<int>res(po.size());
+        unordered_map<int,int>pos;
+        for(int i=0;i<po.size();i++)pos[po[i]]=i;
+        for(int j=0;j<h.size();j++){
+            res[pos[h[j].first]]=h[j].second;
+        }
+        vector<int> ans;
+        for(auto f:res)if(f)ans.push_back(f);
+        return ans;
+    }
+};