leetcode 日经贴，Cpp code -Dungeon Game

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Dungeon Game

//very slow

class Solution {public:    bool can(const vector<vector<int> > &dungeon, int v) {        int n = dungeon.size();        int m = dungeon[0].size();        vector<vector<int> > td = dungeon;        if (td[0][0] + v <= 0) return false;        td[0][0] += v;        int mm = -(1<<20);        for (int j = 1; j < m; ++j) {            if (td[0][j - 1] > 0 && td[0][j - 1] + td[0][j] > 0) {                td[0][j] += td[0][j - 1];            } else {                td[0][j] = mm;            }        }        for (int i = 1; i < n; ++i) {            if (td[i - 1][0] > 0 && td[i - 1][0] + td[i][0] > 0) {                td[i][0] += td[i - 1][0];            } else {                td[i][0] = mm;            }        }        for (int i = 1; i < n; ++i) {            for (int j = 1; j < m; ++j) {                int v1 = mm, v2 = mm;                if (td[i - 1][j] > 0 && td[i - 1][j] + td[i][j] > 0) {                    v1 = td[i - 1][j] + td[i][j];                }                if (td[i][j - 1] > 0 && td[i][j - 1] + td[i][j] > 0) {                    v2 = td[i][j - 1] + td[i][j];                }                td[i][j] = max(v1, v2);            }        }        return td[n - 1][m - 1] > 0;    }    int calculateMinimumHP(vector<vector<int> > &dungeon) {        int n = dungeon.size();        if (n == 0) return 1;        int m = dungeon[0].size();        if (m == 0) return 1;        int low = 1, high = -1, mid = -1;        for (int i = 0; i < n; ++i) {            for (int j = 0; j < m; ++j) {                if (dungeon[i][j] < 0) {                    high += dungeon[i][j];                }            }        }        high = -high;        while (low < high) {            int mid = (low + high) / 2;            if(can(dungeon, mid)) {                high = mid;            } else {                low = mid + 1;            }        }        return high;    }};

//dp[i][j] mean the minimun value needed to reach (n-1, m-1) from (i, j)class Solution {public:    int calculateMinimumHP(vector<vector<int> > &dungeon) {        int n = dungeon.size();        if (n == 0) return 1;        int m = dungeon[0].size();        if (m == 0) return 1;        vector<vector<int> > dp;        dp.resize(n);        for (int i = 0; i < n; ++i) {            dp[i].resize(m);        }        dp[n - 1][m - 1] = max(1, 1 - dungeon[n - 1][m - 1]);        for (int i = n - 1; i >= 0; --i) {            for (int j = m - 1; j >= 0; --j) {                if (i == n - 1 && j == m - 1)                    continue;                if (i == n - 1) {                    dp[i][j] = max(1, dp[i][j + 1] - dungeon[i][j]);                } else if (j == m - 1) {                    dp[i][j] = max(1, dp[i + 1][j] - dungeon[i][j]);                } else {                    dp[i][j] = max(1, min(dp[i][j + 1], dp[i + 1][j]) - dungeon[i][j]);                }            }        }        return dp[0][0];    }};

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