LeetCode-in-Java
474. Ones and Zeroes
Medium
You are given an array of binary strings strs and two integers m and n.
Return the size of the largest subset of strs such that there are at most m 0’s and n 1’s in the subset.
A set x is a subset of a set y if all elements of x are also elements of y.
Example 1:
Input: strs = [“10”,”0001”,”111001”,”1”,”0”], m = 5, n = 3
Output: 4
Explanation: The largest subset with at most 5 0’s and 3 1’s is {“10”, “0001”, “1”, “0”}, so the answer is 4. Other valid but smaller subsets include {“0001”, “1”} and {“10”, “1”, “0”}. {“111001”} is an invalid subset because it contains 4 1’s, greater than the maximum of 3.
Example 2:
Input: strs = [“10”,”0”,”1”], m = 1, n = 1
Output: 2
Explanation: The largest subset is {“0”, “1”}, so the answer is 2.
Constraints:
1 <= strs.length <= 6001 <= strs[i].length <= 100strs[i]consists only of digits'0'and'1'.1 <= m, n <= 100
Solution
public class Solution {
/*
* The problem can be interpreted as:
* What's the max number of str can we pick from strs with limitation of m "0"s and n "1"s.
*
* Thus we can define dp[i][j] as it stands for max number of str can we pick from strs with limitation
* of i "0"s and j "1"s.
*
* For each str, assume it has a "0"s and b "1"s, we update the dp array iteratively
* and set dp[i][j] = Math.max(dp[i][j], dp[i - a][j - b] + 1).
* So at the end, dp[m][n] is the answer.
*/
public int findMaxForm(String[] strs, int m, int n) {
int[][] dp = new int[m + 1][n + 1];
for (String str : strs) {
int[] count = count(str);
for (int i = m; i >= count[0]; i--) {
for (int j = n; j >= count[1]; j--) {
dp[i][j] = Math.max(dp[i][j], dp[i - count[0]][j - count[1]] + 1);
}
}
}
return dp[m][n];
}
private int[] count(String str) {
int[] res = new int[2];
for (int i = 0; i < str.length(); i++) {
res[str.charAt(i) - '0']++;
}
return res;
}
}