代码随想录算法训练营Day45|贪心算法5

代码随想录算法训练营Day45|贪心算法5

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一、1049. 最后一块石头的重量 II

在这里插入代码片class Solution {
    public int lastStoneWeightII(int[] stones) {
        int sum=0;
        for(int s:stones){
            sum+=s;
        }
        int target=sum/2;
        int len=stones.length;
        int dp[][]=new int[len][target+1];
        for(int j=stones[0];j<=target;j++){
            dp[0][j]=stones[0];
        }
         for (int i = 1; i < len; i++) {
            for (int j = 1; j <= target; j++) {
                if (j >= stones[i]) {
             dp[i][j] = Math.max(dp[i - 1][j], dp[i - 1][j - stones[i]] + stones[i]);
                } else {
                    dp[i][j] = dp[i - 1][j];
                }
            }
        }

        System.out.println(dp[stones.length - 1][target]);
        return (sum - dp[stones.length - 1][target]) - dp[stones.length - 1][target];
    }
}

二、494. 目标和

class Solution {
    public int findTargetSumWays(int[] nums, int target) {
        int sum = 0;
        for(int i = 0; i < nums.length; i++) {
            sum += nums[i];
        }


        if(sum < Math.abs(target)){
            return 0;
        }


        if((sum + target) % 2 != 0) {
            return 0;
        }

        int left = (sum + target) / 2;
        
        int[][] dp = new int[nums.length][left + 1];

    
        for(int j = 0; j <= left; j++) {
            if(nums[0] == j) {
                dp[0][j] = 1;
            }
        }
        int numZeros = 0;
        for(int i = 0; i < nums.length; i++) {
            if(nums[i] == 0) {
                numZeros++;
            }
            dp[i][0] = (int) Math.pow(2, numZeros);

        }

    
        for(int i = 1; i < nums.length; i++) {
            for(int j = 1; j <= left; j++) {
                if(nums[i] > j) {
                    dp[i][j] = dp[i - 1][j];
                } else {
                    dp[i][j] = dp[i - 1][j] + dp[i - 1][j - nums[i]];
                }
            }
        }


        return dp[nums.length - 1][left];
        
    }
}

三、474. 一和零

class Solution {
    public int findMaxForm(String[] strs, int m, int n) {
        //dp[i][j]表示i个0和j个1时的最大子集
        int[][] dp = new int[m + 1][n + 1];
        int oneNum, zeroNum;
        for (String str : strs) {
            oneNum = 0;
            zeroNum = 0;
            for (char ch : str.toCharArray()) {
                if (ch == '0') {
                    zeroNum++;
                } else {
                    oneNum++;
                }
            }
       
            for (int i = m; i >= zeroNum; i--) {
                for (int j = n; j >= oneNum; j--) {
                    dp[i][j] = Math.max(dp[i][j], dp[i - zeroNum][j - oneNum] + 1);
                }
            }
        }
        return dp[m][n];
    }
}