LintCode 669 给出不同面额的硬币以及一个总金额. 写一个方法来计算给出的总金额可以换取的最少的硬币数量. 如果已有硬币的任意组合均无法与总金额面额相等, 那么返回 -1.

class Solution {
public:
    /**
     * @param coins: a list of integer
     * @param amount: a total amount of money amount
     * @return: the fewest number of coins that you need to make up
     */
    int coinChange(vector &coins, int amount) {
        // write your code here
        vector dp(amount+1, 0x7fffffff-1);
        dp[0] = 0;
        for (int i = 0; i < coins.size(); i++) {
            int val = coins[i];
            for (int j = 1; j <= amount; j++)
                if (j >= val)
                    dp[j] = min(dp[j], dp[j-val]+1);

        }
        return dp[amount] == 0x7fffffff-1 ? -1 : dp[amount];
    }
};