最长上升连续子序列 II

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给定一个整数矩阵（其中，有 n 行， m 列），请找出矩阵中的最长上升连续子序列。（最长上升连续子序列可从任意行或任意列开始，向上/下/左/右任意方向移动）。

样例

给定一个矩阵

[  [1 ,2 ,3 ,4 ,5],  [16,17,24,23,6],  [15,18,25,22,7],  [14,19,20,21,8],  [13,12,11,10,9]]

返回 25

挑战

O(nm) 时间复杂度及存储。

class Solution {public:    /**     * @param A an integer matrix     * @return  an integer     */    int longestIncreasingContinuousSubsequenceII(vector<vector<int>>& A) {        // Write your code here        int m = A.size();    int n = A[0].size();    memset(buf, 0, m*n*sizeof(int));    for (int i = 0; i < m; i++)    {    for (int j = 0; j < n; j++)    {    if (buf[i][j] != 0)    {    continue;    }    int beginX = i;    int beginY = j;    int maxLen = 1;    findBegin(A, m, n, i, j, beginX, beginY, 1, maxLen);    buf[beginX][beginY] = 1;    visit(A, m, n, beginX, beginY);    }    }    int result = 0;    for (int i = 0; i < m; i++)    {    for (int j = 0; j < n; j++)    {    if (buf[i][j] > result)    {    result = buf[i][j];    }    }    }    return result;    }private:    void findBegin(vector<vector<int> > &A, int m, int n, int i, int j,     int &beginX, int &beginY, int len, int &maxLen)    {    if (i-1 >= 0)    {    if (A[i-1][j] == A[i][j]-1)    {    if (len+1 > maxLen)    {    beginX = i-1;    beginY = j;    maxLen = len+1;    findBegin(A, m, n, i-1, j, beginX, beginY, len+1, maxLen);    }    }    }    if (i+1 < m)    {    if (A[i+1][j] == A[i][j]-1)    {    if (len+1 > maxLen)    {    beginX = i+1;    beginY = j;    maxLen = len+1;    findBegin(A, m, n, i+1, j, beginX, beginY, len+1, maxLen);    }    }    }    if (j-1 >= 0)    {    if (A[i][j-1] == A[i][j]-1)    {    if (len+1 > maxLen)    {    beginX = i;    beginY = j-1;    maxLen = len+1;    findBegin(A, m, n, i, j-1, beginX, beginY, len+1, maxLen);    }    }    }    if (j+1 < n)    {    if (A[i][j+1] == A[i][j]-1)    {    if (len+1 > maxLen)    {    beginX = i;    beginY = j+1;    maxLen = len+1;    findBegin(A, m, n, i, j+1, beginX, beginY, len+1, maxLen);    }    }    }    }        void visit(vector<vector<int> > &A, int m, int n, int i, int j)    {    if (i-1 >= 0)    {    if (A[i-1][j] == A[i][j]+1)    {    buf[i-1][j] = buf[i][j]+1;    visit(A, m, n, i-1, j);    }    }    if (i+1 < m)    {    if (A[i+1][j] == A[i][j]+1)    {    buf[i+1][j] = buf[i][j]+1;    visit(A, m, n, i+1, j);    }    }    if (j-1 >= 0)    {    if (A[i][j-1] == A[i][j]+1)    {    buf[i][j-1] = buf[i][j]+1;    visit(A, m, n, i, j-1);    }    }    if (j+1 < n)    {    if (A[i][j+1] == A[i][j]+1)    {    buf[i][j+1] = buf[i][j]+1;    visit(A, m, n, i, j+1);    }    }    }    int buf[100][100];};

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