第 377 场周赛虚拟参赛记录及补题

最小数字游戏 3

• 题目
  - 思路
  模拟
• 代码

class Solution {
public:
    vector numberGame(vector& nums) {
        sort(nums.begin(),nums.end());
        vector ans;
        for (int i = 0;i < nums.size();i ++) 
            if (i&1)
                ans.push_back(nums[i-1]);
            else 
                ans.push_back(nums[i+1]);
        return ans;
    }
};

移除栅栏得到的正方形田地的最大面积 4

• 思路
  - 思路
  细节题，把所有的空隙全考虑一遍。
• 代码

class Solution {
public:
    int maximizeSquareArea(int m, int n, vector& hFences, vector& vFences) {
        long long ans = 0;
        sort(hFences.begin(),hFences.end());
        sort(vFences.begin(),vFences.end());
        int hlen = hFences.size(),vlen = vFences.size();
        int x = 0;
        vector hc,vc;
        hc.push_back(m-1);
        for (int i = 0;i < hlen;i ++) {
            hc.push_back(hFences[i]-1);
            for (int j = i + 1;j < hlen;j ++) 
                hc.push_back(hFences[j]-hFences[i]);
            hc.push_back(m-hFences[i]);
        } 
        vc.push_back(n-1);
        for (int i = 0;i < vlen;i ++) {
            vc.push_back(vFences[i]-1);
            for (int j = i + 1;j < vlen;j ++) 
                vc.push_back(vFences[j]-vFences[i]);
            vc.push_back(n-vFences[i]);
        }
        sort(hc.begin(),hc.end());
        sort(vc.begin(),vc.end());
        int l = hc.size()-1,r = vc.size()-1;
        while (l >= 0&&r >= 0&&hc[l] != vc[r]) {
            if (hc[l] > vc[r]) l --;
            else r --;
        }
        if (l >= 0 && r >= 0) {
            ans = 1ll*hc[l]*hc[l];
            return ans%(1000000007);
        } else {
            return -1;
        }
    }
};

转换字符串的最小成本 I 5

• 题目
  - 示例
  
• 思路
  最短路，先处理26个字母之间的最短路。这样复杂度就是O(262626);
  
  
• 代码

class Solution {
public:
    long long minimumCost(string source, string target, vector<char> &original, vector<char> &changed, vector<int> &cost) {
        int dis[26][26];
        memset(dis, 0x3f, sizeof(dis));
        for (int i = 0; i < 26; i++) {
            dis[i][i] = 0;
        }
        for (int i = 0; i < cost.size(); i++) {
            int x = original[i] - 'a';
            int y = changed[i] - 'a';
            dis[x][y] = min(dis[x][y], cost[i]);
        }
        for (int k = 0; k < 26; k++) {
            for (int i = 0; i < 26; i++) {
                for (int j = 0; j < 26; j++) {
                    dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]);
                }
            }
        }

        long long ans = 0;
        for (int i = 0; i < source.length(); i++) {
            int d = dis[source[i] - 'a'][target[i] - 'a'];
            if (d == 0x3f3f3f3f) {
                return -1;
            }
            ans += d;
        }
        return ans;
    }
};

转换字符串的最小成本 II 6

• 题意
  
• 思路
  
• 代码

int f[200005][26], g[200005];

class Solution {
public:
    long long minimumCost(string source, string target, vector<string>& original, vector<string>& changed, vector<int>& cost) {
        int n = original.size() * 2;
        long long d[n][n];
        memset(d, 0x3f, sizeof(d));
        long long inf = 0x3f3f3f3f3f3f3f3fll;
        
        int p = 1;
        memset(f[0], -1, sizeof(f[0]));
        g[0] = -1;
        
        auto insert = [&](string& s) {
            int cur = 0;
            for(char c : s) {
                if(f[cur][c-'a'] == -1) {
                    f[cur][c-'a'] = p;
                    memset(f[p], -1, sizeof(f[p]));
                    g[p] = -1;
                    p++;
                }
                cur = f[cur][c-'a'];
            }
            return cur;
        };
        
        int m = 0;
        for(int i = 0; i < original.size(); ++i) {
            int from = insert(original[i]), to = insert(changed[i]);
            if(g[from] == -1)
                g[from] = m++;
            if(g[to] == -1)
                g[to] = m++;
            d[g[from]][g[to]] = min(d[g[from]][g[to]], (long long)cost[i]);
        }
        
        for(int k = 0; k < m; ++k) {
            for(int i = 0; i < m; ++i) {
                for(int j = 0; j < m; ++j) {
                    d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
                }
            }
        }
        
        long long dp[source.size() + 1];
        dp[source.size()] = 0;
        
        for(int i = source.size() - 1; i >= 0; --i) {
            dp[i] = inf;
            if(source[i] == target[i])
                dp[i] = dp[i+1];
            for(int j = i, cur1 = 0, cur2 = 0; j < source.size(); ++j) {
                cur1 = f[cur1][source[j]-'a'];
                cur2 = f[cur2][target[j]-'a'];
                if(cur1 == -1 || cur2 == -1) break;
                if(g[cur1] != -1 && g[cur2] != -1)
                    dp[i] = min(dp[i], d[g[cur1]][g[cur2]] + dp[j+1]);
            }
        }
        
        if(dp[0] >= inf) return -1;
        return dp[0];
    }
};