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#include "leetcode.h"
class Solution {
public:
vector<vector<int>> updateMatrix(vector<vector<int>> &mat) {
int m = mat.size(), n = mat[0].size();
vector<vector<int>> ans(m, vector<int>(n, INT_MAX));
queue<pair<int, int>> qp;
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (mat[i][j] == 0) {
ans[i][j] = 0;
qp.push({i, j});
}
}
}
vector<pair<int, int>> vp{{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
while (!qp.empty()) {
auto curr = qp.front();
qp.pop();
int currX = curr.first, currY = curr.second;
for (auto dirr : vp) {
int x = currX + dirr.first, y = currY + dirr.second;
if (x >= 0 && x < m && y >= 0 && y < n) {
if (ans[x][y] > ans[currX][currY] + 1) {
ans[x][y] = ans[currX][currY] + 1;
qp.push({x, y});
}
}
}
}
return ans;
}
};
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