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package 第01期.mca_08_dp;
public class Code02_SumWays {
// arr中都是正数，sum也是正数
// 求组成sum的方法数量
public static int sumWays(int[] arr, int sum) {
int n = arr.length;
if (n == 0) {
return sum == 0 ? 1 : 0;
}
int[][] dp = new int[n][sum + 1];
for (int i = 0; i < n; i++) {
dp[i][0] = 1;
if (arr[0] <= sum) {
dp[0][arr[0]] = 1;
for (int i = 1; i < n; i++) {
for (int j = 1; j <= sum; j++) {
dp[i][j] = dp[i - 1][j] + (j - arr[i] >= 0 ? dp[i - 1][j - arr[i]] : 0);
return dp[n - 1][sum];
