added leetcode problems - 75-sort_colors.cpp, 16-3sum_closest.cpp, 31-next_permutation.cpp, 155-min_stack.cpp, 84-Largest_Rectangle_in_Histogram.cpp issue #27

16.cpp

@@ -0,0 +1,31 @@
+class Solution {
+public:
+    int threeSumClosest(vector<int>& A, int target) {
+     sort(A.begin(),A.end());
+    int f,s,t;
+    int res=0;
+    int min_diff =INT_MAX;
+    for(f=0;f<A.size()-2;f++)
+    {
+        s= f+1;
+        t=A.size()-1;
+        while(s<t)
+        { int sum= A.at(f) + A.at(s) + A.at(t);
+          int cur = fabs(sum-target);
+          if(cur<min_diff)
+          {
+              min_diff =cur;
+              res =sum;
+          }
+          if(sum>target)
+           t--;
+           else if(sum<target)
+           s++;
+           else
+           return sum;
+
+        }
+    }
+    return res;
+    }
+};

leetcode/cpp/Array/31.cpp

@@ -0,0 +1,26 @@
+class Solution {
+public:
+    void nextPermutation(vector<int>& A) {
+        int i,j;
+    int n = A.size();
+    for(i = n - 2;i >= 0;i --)
+    {
+        if(A[i] < A[i + 1])
+            break;
+    }
+    if(i == -1)
+    {
+        reverse(A.begin(),A.end());
+        return ;
+    }
+
+    for(j = n - 1;j > i;j --)
+    {
+        if(A[j] > A[i])
+            break;
+    }
+    swap(A[j],A[i]);
+    reverse(A.begin() + i + 1,A.end());
+    return ;
+    }
+};

leetcode/cpp/Array/84.cpp

@@ -0,0 +1,24 @@
+class Solution {
+public:
+int largestRectangleArea(vector<int> &A) {
+    int res = 0;
+    A.push_back(0);
+
+    stack<int> st;
+
+    for(auto i=0; i<A.size(); i++)
+    {
+        if(st.empty() || A[i] >= A[st.top()])
+            st.push(i);
+        else
+        {
+            int j = st.top();
+            st.pop();
+            res = max(res, A[j]*(st.empty() ? i : i - st.top() - 1));
+            i--;
+        }
+    }
+
+    return res;
+}
+};

leetcode/cpp/Stacks/155.cpp

@@ -0,0 +1,49 @@
+class MinStack {
+public:
+    /** initialize your data structure here. */
+    MinStack() {
+
+    }
+     stack<int> st;
+    stack<int> min_st;
+    void push(int x) {
+        st.push(x);
+    int val =x;
+   if(min_st.size()>0 && min_st.top()<x)
+   {
+       val =min_st.top();
+   }
+    min_st.push(val);
+    }
+
+    void pop() {
+       if(!st.empty())
+   { st.pop();
+     min_st.pop();
+   }
+    }
+
+    int top() {
+       if(st.empty())
+    return -1;
+    else
+    return st.top();
+
+    }
+
+    int getMin() {
+        if(st.empty())
+    return -1;
+    else
+    return min_st.top();
+    }
+};
+
+/**
+ * Your MinStack object will be instantiated and called as such:
+ * MinStack* obj = new MinStack();
+ * obj->push(x);
+ * obj->pop();
+ * int param_3 = obj->top();
+ * int param_4 = obj->getMin();
+ */

leetcode/cpp/Two Pointer/16.cpp

@@ -0,0 +1,31 @@
+class Solution {
+public:
+    int threeSumClosest(vector<int>& A, int target) {
+     sort(A.begin(),A.end());
+    int f,s,t;
+    int res=0;
+    int min_diff =INT_MAX;
+    for(f=0;f<A.size()-2;f++)
+    {
+        s= f+1;
+        t=A.size()-1;
+        while(s<t)
+        { int sum= A.at(f) + A.at(s) + A.at(t);
+          int cur = fabs(sum-target);
+          if(cur<min_diff)
+          {
+              min_diff =cur;
+              res =sum;
+          }
+          if(sum>target)
+           t--;
+           else if(sum<target)
+           s++;
+           else
+           return sum;
+
+        }
+    }
+    return res;
+    }
+};

leetcode/cpp/Two Pointer/75.cpp

@@ -1,22 +1,21 @@
-class Solution {
-public:
-    void sortColors(vector<int>& nums) {
-        int  low=0,mid=0,high=nums.size()-1;
-        while(mid<=high){
-
-            if(nums[mid]==0)
-            {
-              swap(nums[low],nums[mid]);
-                low++,mid++;
-            }
-            else if(nums[mid]==1)
-            {
-                mid++;
-            }
-            else{
-                swap(nums[mid],nums[high]);
-                high--;
-            }
-        }
-    }
-};
+class Solution {
+public:
+    void sortColors(vector<int>& A) {
+        int count_0=0,count_1=0,count_2=0;
+    for(int i=0;i<A.size();i++)
+    {
+        if(A[i]==0)
+         count_0++;
+        else if(A[i]==1)
+         count_1++;
+        else if(A[i]==2)
+         count_2++;
+    }
+    for(int i=0;i<count_0;i++)
+      A[i]=0;
+    for(int i=count_0;i<count_0+count_1;i++)
+      A[i]=1;
+    for(int i=count_1+count_0;i<count_0+count_1+count_2;i++)
+      A[i]=2;
+    }
+};