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StoneGame

StoneGame全家福

1140. Stone Game II

zero sum game

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int[][][] memo;
int[] piles;
int n;
public int stoneGameII(int[] piles) {
n=piles.length;
//i, m, turn
//i: already settled i stones
memo=new int[n+1][n+1][2];
this.piles=piles;
for (int i = 0; i <= n; i++) {
for (int j = 0; j <= n; j++) {
for (int k = 0; k < 2; k++) {
memo[i][j][k]=-1;
}
}
}
return dp(0,1,0);
}

int dp(int i, int m, int turn){
if(i>=n){
return 0;
}
if(memo[i][m][turn]!=-1){
return memo[i][m][turn];
}
int sum=0;
int res= turn==0 ? 0 : Integer.MAX_VALUE;
//i+x <= n
//x <= n-i
for(int x=1; x<=Math.min(n-i,2*m); x++){
sum+=piles[i+x-1];
if(turn==0){
res=Math.max(res,sum+dp(i+x,Math.max(m,x),1));
}else{
res=Math.min(res,dp(i+x,Math.max(m,x),0));
}
}
return memo[i][m][turn]=res;
}