for(int i = 1 ; i <= n ; i ++){
	dp[i][i] = 0; //s[][]的初始值
	s[i][i] = i;
} 
for(int len = 2; len <= n ; len ++)
	for(int i = 1 ; i <= n - len + 1; i ++){
		int j = i + len - 1;
		for(k = s[i][j - 1]; k <= s[i + 1][j]; k ++){ //缩小循环范围
			if(dp[i][j] > dp[i][k] + dp[k + 1][j] + w[i][j]){//是否更优
				dp[i][j] = dp[i][k] + dp[k + 1][j] + w[i][j];
				s[i][j] = k;//更新最佳分割点
			}
		}
	}