Added 486 leetcode solution Predict the winner cpp

Author: nitishjatwar21

486. Leetcode Predict the Winner.cpp

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+
+/* Approach: As both the players are equally strong, both will try to reduce the possibility of winning of each 
+other. Now let’s see how the opponent can achieve this.
+
+There are two choices:  
+
+The user chooses the ‘ith’ coin with value ‘Vi’: The opponent either chooses (i+1)th coin or jth coin. 
+The opponent intends to choose the coin which leaves the user with minimum value. 
+i.e. The user can collect the value Vi + min(F(i+2, j), F(i+1, j-1) ). 
+ 
+coinGame1
+
+The user chooses the ‘jth’ coin with value ‘Vj’: The opponent either chooses ‘ith’ coin or ‘(j-1)th’ coin. 
+The opponent intends to choose the coin which leaves the user with minimum value, i.e. the user can 
+collect the value Vj + min(F(i+1, j-1), F(i, j-2) ). 
+*/
+
+
+
+
+class Solution {
+public:
+    int dp[30][30];
+    int find(int l,int r,vector<int>& v){
+        if(dp[l][r]!=-1)return dp[l][r];
+        if(l==r)return dp[l][r]=v[l];
+        if(r==l+1)return dp[l][r]=max(v[l],v[r]);
+        return dp[l][r]=max(v[l] + min(find(l+2,r,v), find(l+1,r-1,v) ), v[r] + min( find(l,r-2,v), find(l+1,r-1,v) ) );
+    }
+    bool PredictTheWinner(vector<int>& nums) {
+        memset(dp,-1,sizeof(dp));
+        int n=nums.size();
+        int s=accumulate(nums.begin(),nums.end(),0);
+        int a=find(0,n-1,nums)*2;
+        return (a>=s)?true:false;
+    }
+};