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Space Optimized solution for 3459. #100

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Space Optimized solution for 3459. #100

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19 changes: 9 additions & 10 deletions solutions/3459. Length of Longest V-Shaped Diagonal Segment/3459.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3,10 +3,10 @@ class Solution {
int lenOfVDiagonal(vector<vector<int>>& grid) {
const int m = grid.size();
const int n = grid[0].size();
vector<vector<vector<vector<vector<int>>>>> mem(
m, vector<vector<vector<vector<int>>>>(
n, vector<vector<vector<int>>>(
2, vector<vector<int>>(2, vector<int>(4, -1)))));
vector<vector<vector<vector<int>>>> mem(
m, vector<vector<vector<int>>>(
n, vector<vector<int>>(
2, vector<int>(4, -1))));
int res = 0;

for (int i = 0; i < m; ++i)
Expand All @@ -25,15 +25,14 @@ class Solution {
static constexpr int kDirs[4][2] = {{-1, 1}, {1, 1}, {1, -1}, {-1, -1}};

int dfs(const vector<vector<int>>& grid, int i, int j, bool turned, int num,
int dir, vector<vector<vector<vector<vector<int>>>>>& mem) {
int dir, vector<vector<vector<vector<int>>>>& mem) {
if (i < 0 || i == grid.size() || j < 0 || j == grid[0].size())
return 0;
if (grid[i][j] != num)
return 0;

const int hashNum = max(0, num - 1);
if (mem[i][j][turned][hashNum][dir] != -1)
return mem[i][j][turned][hashNum][dir];
if (mem[i][j][turned][dir] != -1)
return mem[i][j][turned][dir];

const int nextNum = num == 2 ? 0 : 2;
const auto& [dx, dy] = kDirs[dir];
Expand All @@ -42,10 +41,10 @@ class Solution {
if (!turned) {
const int nextDir = (dir + 1) % 4;
const auto& [nextDx, nextDy] = kDirs[nextDir];
res = max(res, 1 + dfs(grid, i + nextDx, j + nextDy, /*turned=*/true,
res = max(res, 1 + dfs(grid, i + nextDx, j + nextDy,/*turned=*/true,
nextNum, nextDir, mem));
}

return mem[i][j][turned][hashNum][dir] = res;
return mem[i][j][turned][dir] = res;
}
};