refactory the code to make it a bit readable

Author: haoel

algorithms/cpp/minimumWindowSubstring/minimumWindowSubstring.cpp

@@ -31,75 +31,82 @@ using namespace std;
 
 #define INT_MAX      2147483647
 
-string minWindow(string S, string T) {
+string minWindow(string s, string t) {
     string win;
-    if (S.size()<=0 || T.size()<=0 || T.size() > S.size()) return win;
+    if (s.size()<=0 || t.size()<=0 || t.size() > s.size()) return win;
     /*
      * Declare two "hash map" for ASCII chars
-     *   f[]: represents the char found in string S
-     *   m[]: stores the chars in string T
+     *   window[]: represents the char found in string S
+     *   dict[]: stores the chars in string T
      */    
     const int MAX_CHARS = 256;
-    int f[MAX_CHARS], m[MAX_CHARS];
-    
+    int window[MAX_CHARS], dict[MAX_CHARS];
+
     const int NOT_EXISTED   = -1;
     const int NOT_FOUND     =  0;
-    memset(m, NOT_EXISTED, sizeof(m));
-    memset(f, NOT_EXISTED, sizeof(f));
+    memset(dict, NOT_EXISTED, sizeof(dict));
+    memset(window, NOT_EXISTED, sizeof(window));
 
     /* 
-     *  Go through the T, and inital the m[] and f[] 
+     *  Go through the T, and inital the dict[] and window[] 
      *  Notes: a same char can be appeared multiple times.
      */
-    for(int i=0; i<T.size(); i++) {
-        m[T[i]]==NOT_EXISTED ? m[T[i]]=1 : m[T[i]]++ ; 
-        f[T[i]] = NOT_FOUND; 
+    for(int i=0; i<t.size(); i++) {
+        dict[t[i]]==NOT_EXISTED ? dict[t[i]]=1 : dict[t[i]]++ ; 
+        window[t[i]] = NOT_FOUND; 
     }
 
     int start =-1;
     int winSize = INT_MAX;
     int letterFound = 0;
-    int begin = 0;
-    for(int i=0; i<S.size(); i++) {
-        /* if S[i] is existed in T*/ 
-        if ( m[S[i]] != NOT_EXISTED ){
-            char ch = S[i];
-            f[ch]++;
-
-            /* if one char has been found enough times, then do not do letterFound++ */
-            if (f[ch] <= m[ch]) {
-                letterFound++;
-            }
-            if ( letterFound >= T.size() ) {
-                /* 
-                 * Find the beginning of the window
-                 * 1) f[S[begin]] == NOT_EXISTED  ===> the char at the `begin` is not in T
-                 * 2) f[S[begin]] > m[S[begin]]   ===> a same char appeared more than excepted.
-                 */
-                while ( f[S[begin]] == NOT_EXISTED || f[S[begin]] > m[S[begin]] ) { 
-                    if ( f[S[begin]] > m[S[begin]] ) {
-                        f[S[begin]]--;
-                    }   
-                    begin++;
+    int left = 0;
+
+    for(int right=0; right<s.size(); right++) {
+        if ( dict[s[right]] == NOT_EXISTED ){
+            continue;
+        }
+
+        /* if s[i] is existed in `t` */ 
+        char chr = s[right];
+        window[chr]++;
+
+        /* if one char has been found enough times, then do not do letterFound++ */
+        if (window[chr] <= dict[chr]) {
+            letterFound++;
+        }
+
+        if ( letterFound >= t.size() ) {
+            /* 
+             * Find the left of the window - try to make the window smaller
+             * 1) windows[S[left]] == NOT_EXISTED  ===> the char at the `left` is not in T
+             * 2) window[S[left]] > dict[S[left]]   ===> a same char appeared more than excepted.
+             */
+            char chl = s[left];
+            while ( window[chl] == NOT_EXISTED || window[chl] > dict[chl] ) { 
+                if (dict[chl] != NOT_EXISTED  ) {
+                    //move the left of window
+                    window[chl]--; 
+                    // reduce the number of letters found
+                    if (window[chl] < dict[chl] ) letterFound--;
                 }
-                /* Calculate the minimized window size */
-                if(winSize > i - begin + 1){
-                    start = begin;
-                    winSize = i - begin + 1;
-                }     
-                
+                chl = s[++left];
+            }
+
+            /* Calculate the minimized window size */
+            if(winSize > right - left + 1){
+                start = left;
+                winSize = right - left + 1;
             }
-            
+
         }
     }
 
     if (start>=0 && winSize>0) {
-        win = S.substr(start, winSize);
+        win = s.substr(start, winSize);
     }
     return win;
 }
 
-
 int main(int argc, char**argv)
 {
     string S = "ADOBECODEBANC";