leetcode322. Coin Change

辣鸡如我，居然现在完全背包还要想这么久

https://leetcode.com/problems/coin-change/

You are given coins of different denominations and a total amount of money amount. Write a function to compute the fewest number of coins that you need to make up that amount. If that amount of money cannot be made up by any combination of the coins, return -1.

Example 1:

Input: coins = [1, 2, 5], amount = 11
Output: 3 
Explanation: 11 = 5 + 5 + 1

Example 2:

Input: coins = [2], amount = 3
Output: -1

class Solution {
public:
    int coinChange(vector<int>& coins, int amount) {
        int dp[20000];
        for (int i = 1; i < 20000; i ++)
            dp[i] = 0x3f3f3f3f;
        dp[0] = 0;
        for (int i = 1; i <= amount ; i ++) {
            for (int j = 0; j < coins.size() ; j ++) {
                if (coins[j]  <= i) {
                    dp[i] = min(dp[i - coins[j]] + 1, dp[i]);
                }
            }
        }
        if (dp[amount] != 0x3f3f3f3f)
            return dp[amount];
        else
            return -1;
    }
};